Data Structure and Algorithms - Linked List


If arrays accommodate similar types of data types, linked lists consist of elements with different data types that are also arranged sequentially.

But how are these linked lists created?

A linked list is a collection of “nodes” connected together via links. These nodes consist of the data to be stored and a pointer to the address of the next node within the linked list. In the case of arrays, the size is limited to the definition, but in linked lists, there is no defined size. Any amount of data can be stored in it and can be deleted from it.

There are three types of linked lists −

  • Singly Linked List − The nodes only point to the address of the next node in the list.

  • Doubly Linked List − The nodes point to the addresses of both previous and next nodes.

  • Circular Linked List − The last node in the list will point to the first node in the list. It can either be singly linked or doubly linked.

Linked List Representation

Linked list can be visualized as a chain of nodes, where every node points to the next node.

Linked List Representation

As per the above illustration, following are the important points to be considered.

  • Linked List contains a link element called first (head).

  • Each link carries a data field(s) and a link field called next.

  • Each link is linked with its next link using its next link.

  • Last link carries a link as null to mark the end of the list.

Types of Linked List

Following are the various types of linked list.

Singly Linked Lists

Singly linked lists contain two “buckets” in one node; one bucket holds the data and the other bucket holds the address of the next node of the list. Traversals can be done in one direction only as there is only a single link between two nodes of the same list.

Singly Linked Lists

Doubly Linked Lists

Doubly Linked Lists contain three “buckets” in one node; one bucket holds the data and the other buckets hold the addresses of the previous and next nodes in the list. The list is traversed twice as the nodes in the list are connected to each other from both sides.

Doubly Linked Lists

Circular Linked Lists

Circular linked lists can exist in both singly linked list and doubly linked list.

Since the last node and the first node of the circular linked list are connected, the traversal in this linked list will go on forever until it is broken.

Circular_Linked_Lists

Basic Operations in the Linked Lists

The basic operations in the linked lists are insertion, deletion, searching, display, and deleting an element at a given key. These operations are performed on Singly Linked Lists as given below −

  • Insertion − Adds an element at the beginning of the list.

  • Deletion − Deletes an element at the beginning of the list.

  • Display − Displays the complete list.

  • Search − Searches an element using the given key.

  • Delete − Deletes an element using the given key.

Insertion Operation

Adding a new node in linked list is a more than one step activity. We shall learn this with diagrams here. First, create a node using the same structure and find the location where it has to be inserted.

Insertion Operation

Imagine that we are inserting a node B (NewNode), between A (LeftNode) and C (RightNode). Then point B.next to C −

NewNode.next −> RightNode;

It should look like this −

Inserting A Node

Now, the next node at the left should point to the new node.

LeftNode.next −> NewNode;
Point To The New Node

This will put the new node in the middle of the two. The new list should look like this −

Insertion in linked list can be done in three different ways. They are explained as follows −

Insertion at Beginning

In this operation, we are adding an element at the beginning of the list.

Algorithm

1. START
2. Create a node to store the data
3. Check if the list is empty
4. If the list is empty, add the data to the node and assign the head pointer to it.
5 If the list is not empty, add the data to a node and link to the current head. Assign the head to the newly added node.
6. END

Example

Following are the implementations of this operation in various programming languages −

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");
   
   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

//insertion at the beginning
void insertatbegin(int data){
   
   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   
   // point it to old first node
   lk->next = head;
   
   //point first to new first node
   head = lk;
}
void main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(44);
   insertatbegin(50);
   printf("Linked List: ");
   
   // print list
   printList();
}

Output

Linked List: 
[ 50  44  30  22  12 ]
#include <bits/stdc++.h>
#include <string>
using namespace std;
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   cout << "\n[";
   
   //start from the beginning
   while(p != NULL) {
      cout << " " << p->data << " ";
      p = p->next;
   }
   cout << "]";
}

//insertion at the beginning
void insertatbegin(int data){
   
   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   
   // point it to old first node
   lk->next = head;
   
   //point first to new first node
   head = lk;
}
int main(){
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(44);
   insertatbegin(50);
   cout << "Linked List: ";
   
   // print list
   printList();
}

Output

Linked List: 
[ 50  44  30  22  12 ]
public class Linked_List {
   static class node {
      int data;
      node next;
      node (int value) {
         data = value;
         next = null;
      }
   }
   static node head;
   
   // display the list
   static void printList() {
      node p = head;
      System.out.print("\n[");
   
      //start from the beginning
      while(p != null) {
         System.out.print(" " + p.data + " ");
         p = p.next;
      }
      System.out.print("]");
   }

   //insertion at the beginning
   static void insertatbegin(int data) {

      //create a link
      node lk = new node(data);;

      // point it to old first node
      lk.next = head;

      //point first to new first node
      head = lk;
   }
   public static void main(String args[]) {
      int k=0;
      insertatbegin(12);
      insertatbegin(22);
      insertatbegin(30);
      insertatbegin(44);
      insertatbegin(50);
      insertatbegin(33);
      System.out.println("Linked List: ");
      
      // print list
      printList();
   }
}

Output

Linked List: 

[33  50  44  30  22  12 ]
class Node:
   def __init__(self, data=None):
      self.data = data
      self.next = None
class SLL:
   def __init__(self):
      self.head = None

# Print the linked list
   def listprint(self):
      printval = self.head
      print("Linked List: ")
      while printval is not None:
         print (printval.data)
         printval = printval.next
   def AddAtBeginning(self,newdata):
      NewNode = Node(newdata)

      # Update the new nodes next val to existing node
      NewNode.next = self.head
      self.head = NewNode

l1 = SLL()
l1.head = Node("731")
e2 = Node("672")
e3 = Node("63")

l1.head.next = e2
e2.next = e3

l1.AddAtBeginning("122")
l1.listprint()

Output

Linked List: 
122
731
672
63

Insertion at Ending

In this operation, we are adding an element at the ending of the list.

Algorithm

1. START
2. Create a new node and assign the data
3. Find the last node
4. Point the last node to new node
5. END

Example

Following are the implementations of this operation in various programming languages −

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");
   
   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;
   
   //point first to new first node
   head = lk;
}
void insertatend(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   struct node *linkedlist = head;

   // point it to old first node
   while(linkedlist->next != NULL)
      linkedlist = linkedlist->next;

   //point first to new first node
   linkedlist->next = lk;
}
void main(){
   int k=0;
   insertatbegin(12);
   insertatend(22);
   insertatend(30);
   insertatend(44);
   insertatend(50);
   printf("Linked List: ");
   
   // print list
   printList();
}

Output

Linked List:
[ 12 22 30 44 50 ]
#include <bits/stdc++.h>
#include <string>
using namespace std;
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   cout << "\n[";
   
   //start from the beginning
   while(p != NULL) {
      cout << " " << p->data << " ";
      p = p->next;
   }
   cout << "]";
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void insertatend(int data){
   
   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   struct node *linkedlist = head;

   // point it to old first node
   while(linkedlist->next != NULL)
      linkedlist = linkedlist->next;

   //point first to new first node
   linkedlist->next = lk;
}
int main(){
   insertatbegin(12);
   insertatend(22);
   insertatbegin(30);
   insertatend(44);
   insertatbegin(50);
   cout << "Linked List: ";

   // print list
   printList();
}

Output

Linked List: 
[ 50  30  12  22  44 ]
public class Linked_List {
   static class node {
      int data;
      node next;
      node (int value) {
         data = value;
         next = null;
      }
   }
   static node head;

   // display the list
   static void printList() {
      node p = head;
      System.out.print("\n[");

      //start from the beginning
      while(p != null) {
         System.out.print(" " + p.data + " ");
         p = p.next;
      }
      System.out.print("]");
   }

   //insertion at the beginning
   static void insertatbegin(int data) {

      //create a link
      node lk = new node(data);;

      // point it to old first node
      lk.next = head;

      //point first to new first node
      head = lk;
   }
   static void insertatend(int data) {
   
      //create a link
      node lk = new node(data);
      node linkedlist = head;

      // point it to old first node
      while(linkedlist.next != null)
         linkedlist = linkedlist.next;

      //point first to new first node
      linkedlist.next = lk;
   }
   public static void main(String args[]) {
      int k=0;
      insertatbegin(12);
      insertatbegin(22);
      insertatbegin(30);
      insertatend(44);
      insertatend(50);
      insertatend(33);
      System.out.println("Linked List: ");

      // print list
      printList();
   }
}

Output

Linked List: 
[ 30  22  12  44 50  33 ]
class Node:
   def __init__(self, data=None):
      self.data = data
      self.next = None
class LL:
   def __init__(self):
      self.head = None
   def listprint(self):
      val = self.head
      print("Linked List:")
      while val is not None:
         print(val.data)
         val = val.next

l1 = LL()
l1.head = Node("23")
l2 = Node("12")
l3 = Node("7")
l4 = Node("14")
l5 = Node("61")

# Linking the first Node to second node
l1.head.next = l2

# Linking the second Node to third node
l2.next = l3
l3.next = l4
l4.next = l5
l1.listprint()

Output

Linked List:
23
12
7
14
61

Insertion at a Given Position

In this operation, we are adding an element at any position within the list.

Algorithm

1. START
2. Create a new node and assign data to it
3. Iterate until the node at position is found
4. Point first to new first node
5. END

Example

Following are the implementations of this operation in various programming languages −

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");
   
   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void insertafternode(struct node *list, int data){
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   lk->next = list->next;
   list->next = lk;
}
void main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertafternode(head->next, 30);
   printf("Linked List: ");

   // print list
   printList();
}

Output

Linked List:
[ 22 12 30 ]
#include <bits/stdc++.h>
#include <string>
using namespace std;
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   cout << "\n[";
   
   //start from the beginning
   while(p != NULL) {
      cout << " " << p->data << " ";
      p = p->next;
   }
   cout << "]";
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void insertafternode(struct node *list, int data){
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   lk->next = list->next;
   list->next = lk;
}
int main(){
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertafternode(head->next,44);
   insertafternode(head->next->next, 50);
   cout << "Linked List: ";

   // print list
   printList();
}

Output

Linked List: 
[ 30  22  44  50  12 ]
public class Linked_List {
   static class node {
      int data;
      node next;
      node (int value) {
         data = value;
         next = null;
      }
   }
   static node head;

   // display the list
   static void printList() {
      node p = head;
      System.out.print("\n[");

      //start from the beginning
      while(p != null) {
         System.out.print(" " + p.data + " ");
         p = p.next;
      }
      System.out.print("]");
   }

   //insertion at the beginning
   static void insertatbegin(int data) {

      //create a link
      node lk = new node(data);;

      // point it to old first node
      lk.next = head;

      //point first to new first node
      head = lk;
   }
   static void insertafternode(node list, int data) {
      node lk = new node(data);
      lk.next = list.next;
      list.next = lk;
   }
   public static void main(String args[]) {
      int k=0;
      insertatbegin(12);
      insertatbegin(22);
      insertatbegin(30);
      insertatbegin(44);
      insertafternode(head.next, 50);
      insertafternode(head.next.next, 33);
      System.out.println("Linked List: ");

      // print list
      printList();
   }
}

Output

Linked List: 

[44  30  50  33  22  12 ]
class Node:
   def __init__(self, data=None):
      self.data = data
      self.next = None

class SLL:
   def __init__(self):
      self.head = None

# Print the linked list
   def listprint(self):
      printval = self.head
      print("Linked List: ")
      while printval is not None:
         print (printval.data)
         printval = printval.next

   # Function to add node
   def InsertAtPos(self,nodeatpos,newdata):
      if nodeatpos is None:
         print("The mentioned node is absent")
         return
      NewNode = Node(newdata)
      NewNode.next = nodeatpos.next
      nodeatpos.next = NewNode

l1 = SLL()
l1.head = Node("731")
e2 = Node("672")
e3 = Node("63")

l1.head.next = e2
e2.next = e3

l1.InsertAtPos(l1.head.next, "122")
l1.listprint()

Output

Linked List: 
731
672
122
63

Deletion Operation

Deletion is also a more than one step process. We shall learn with pictorial representation. First, locate the target node to be removed, by using searching algorithms.

Deletion Operation

The left (previous) node of the target node now should point to the next node of the target node −

LeftNode.next −> TargetNode.next;
Linked List Deletion

This will remove the link that was pointing to the target node. Now, using the following code, we will remove what the target node is pointing at.

TargetNode.next −> NULL;
Pointing Target Node

We need to use the deleted node. We can keep that in memory otherwise we can simply deallocate memory and wipe off the target node completely.

use deleted node data items

Similar steps should be taken if the node is being inserted at the beginning of the list. While inserting it at the end, the second last node of the list should point to the new node and the new node will point to NULL.

Deletion in linked lists is also performed in three different ways. They are as follows −

Deletion at Beginning

In this deletion operation of the linked, we are deleting an element from the beginning of the list. For this, we point the head to the second node.

Algorithm

1. START
2. Assign the head pointer to the next node in the list
3. END

Example

Following are the implementations of this operation in various programming languages −

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");
   
   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void deleteatbegin(){
   head = head->next;
}
int main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(40);
   insertatbegin(55);
   printf("Linked List: ");
   
   // print list
   printList();
   deleteatbegin();
   printf("\nLinked List after deletion: ");
   
   // print list
   printList();
}

Output

Linked List: 
[ 55  40  30  22  12 ]
Linked List after deletion: 
[ 40  30  22  12 ]
#include <bits/stdc++.h>
#include <string>
using namespace std;
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   cout << "\n[";
   
   //start from the beginning
   while(p != NULL) {
      cout << " " << p->data << " ";
      p = p->next;
   }
   cout << "]";
}

//insertion at the beginning
void insertatbegin(int data){
   
   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void deleteatbegin(){
   head = head->next;
}
int main(){
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(44);
   insertatbegin(50);
   cout << "Linked List: ";

   // print list
   printList();
   deleteatbegin();
   cout << "Linked List after deletion: ";
   printList();
}      

Output

Linked List: 
[ 50  44  30  22  12 ]
Linked List after deletion: 
[ 44  30  22  12 ]
public class Linked_List {
   static class node {
      int data;
      node next;
      node (int value) {
         data = value;
         next = null;
      }
   }
   static node head;
   
   // display the list
   static void printList() {
      node p = head;
      System.out.print("\n[");
      
      //start from the beginning
      while(p != null) {
         System.out.print(" " + p.data + " ");
         p = p.next;
      }
      System.out.print("]");
   }
   
   //insertion at the beginning
   static void insertatbegin(int data) {

      //create a link
      node lk = new node(data);;
      
      // point it to old first node
      lk.next = head;
      
      //point first to new first node
      head = lk;
   }
   static void deleteatbegin() {
      head = head.next;
   }
   public static void main(String args[]) {
      int k=0;
      insertatbegin(12);
      insertatbegin(22);
      insertatbegin(30);
      insertatbegin(44);
      insertatbegin(50);
      insertatbegin(33);
      System.out.println("Linked List: ");
      
      // print list
      printList();
      deleteatbegin();
      System.out.println("\nLinked List after deletion: ");
      
      // print list
      printList();
   }
}

Output

Linked List: 
[ 33  50  44  30  22  12 ]
Linked List after deletion: 

[50  44  30  22  12 ]
#python code for deletion at beginning using linked list.
from typing import Optional
class Node:
    def __init__(self, data: int, next: Optional['Node'] = None):
        self.data = data
        self.next = next
class LinkedList:
    def __init__(self):
        self.head = None
     #display the list
    def print_list(self):
        p = self.head
        print("\n[", end="")
        while p:
            print(f" {p.data} ", end="")
            p = p.next
        print("]")
     #Insertion at the beginning
    def insert_at_begin(self, data: int):
        lk = Node(data)
         #point it to old first node
        lk.next = self.head
        #point firt to new first node
        self.head = lk
    def delete_at_begin(self):
        self.head = self.head.next
if __name__ == "__main__":
    linked_list = LinkedList()
    linked_list.insert_at_begin(12)
    linked_list.insert_at_begin(22)
    linked_list.insert_at_begin(30)
    linked_list.insert_at_begin(44)
    linked_list.insert_at_begin(50)
    #print list
    print("Linked List: ", end="")
    linked_list.print_list()
    linked_list.delete_at_begin()
    print("Linked List after deletion: ", end="")
    linked_list.print_list()

Output

Linked List: 
[ 50  44  30  22  12 ]
Linked List after deletion: 
[ 44  30  22  12 ]

Deletion at Ending

In this deletion operation of the linked, we are deleting an element from the ending of the list.

Algorithm

1. START
2. Iterate until you find the second last element in the list.
3. Assign NULL to the second last element in the list.
4. END

Example

Following are the implementations of this operation in various programming languages −

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");
   
   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

//insertion at the beginning
void insertatbegin(int data){
   
   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void deleteatend(){
   struct node *linkedlist = head;
   while (linkedlist->next->next != NULL)
      linkedlist = linkedlist->next;
   linkedlist->next = NULL;
}
void main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(40);
   insertatbegin(55);
   printf("Linked List: ");
   
   // print list
   printList();
   deleteatend();
   printf("\nLinked List after deletion: ");
   
   // print list
   printList();
}

Output

Linked List: 
[ 55  40  30  22  12 ]
Linked List after deletion: 
[ 55  40  30  22 ]
#include <bits/stdc++.h>
#include <string>
using namespace std;
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// Displaying the list
void printList(){
   struct node *p = head;
   while(p != NULL) {
      cout << " " << p->data << " ";
      p = p->next;
   }
}

// Insertion at the beginning
void insertatbegin(int data){
   
   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   
   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void deleteatend(){
   struct node *linkedlist = head;
   while (linkedlist->next->next != NULL)
      linkedlist = linkedlist->next;
   linkedlist->next = NULL;
}
int main(){
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(44);
   insertatbegin(50);
   cout << "Linked List: ";

   // print list
   printList();
   deleteatend();
   cout << "\nLinked List after deletion: ";
   printList();
}

Output

Linked List:  50  44  30  22  12 
Linked List after deletion:  50  44  30  22 
public class Linked_List {
   static class node {
      int data;
      node next;
      node (int value) {
         data = value;
         next = null;
      }
   }
   static node head;
   
   // display the list
   static void printList() {
      node p = head;
      System.out.print("\n[");
      
      //start from the beginning
      while(p != null) {
         System.out.print(" " + p.data + " ");
         p = p.next;
      }
      System.out.print("]");
   }
   
   //insertion at the beginning
   static void insertatbegin(int data) {
      
      //create a link
      node lk = new node(data);;
      
      // point it to old first node
      lk.next = head;

      //point first to new first node
      head = lk;
   }
   static void deleteatend() {
      node linkedlist = head;
      while (linkedlist.next.next != null)
         linkedlist = linkedlist.next;
      linkedlist.next = null;
   }
   public static void main(String args[]) {
      int k=0;
      insertatbegin(12);
      insertatbegin(22);
      insertatbegin(30);
      insertatbegin(44);
      insertatbegin(50);
      insertatbegin(33);
      System.out.println("Linked List: ");

      // print list
      printList();

      //deleteatbegin();
      deleteatend();
      System.out.println("\nLinked List after deletion: ");

      // print list
      printList();
   }
}

Output

Linked List: 
[ 33  50  44  30  22  12 ]
Linked List after deletion: 

[ 33  50  44  30  22 ]
#python code for deletion at beginning using linked list.
class Node:
    def __init__(self, data=None):
        self.data = data
        self.next = None
class LinkedList:
    def __init__(self):
        self.head = None
 #Displaying the list
    def printList(self):
        p = self.head
        print("\n[", end="")
        while p != None:
            print(" " + str(p.data) + " ", end="")
            p = p.next
        print("]")
 #Insertion at the beginning
    def insertatbegin(self, data):
        #create a link
        lk = Node(data)
        #point it to old first node
        lk.next = self.head
        #point first to new first node
        self.head = lk

    def deleteatend(self):
        linkedlist = self.head
        while linkedlist.next.next != None:
            linkedlist = linkedlist.next
        linkedlist.next = None
if __name__ == "__main__":
    linked_list = LinkedList()
    linked_list.insertatbegin(12)
    linked_list.insertatbegin(22)
    linked_list.insertatbegin(30)
    linked_list.insertatbegin(40)
    linked_list.insertatbegin(55)
    #print list
    print("Linked List: ", end="")
    linked_list.printList()
    linked_list.deleteatend()
    print("Linked List after deletion: ", end="")
    linked_list.printList()

Output

Linked List: 
[ 55  40  30  22  12 ]
Linked List after deletion: 
[ 55  40  30  22 ]

Deletion at a Given Position

In this deletion operation of the linked, we are deleting an element at any position of the list.

Algorithm

1. START
2. Iterate until find the current node at position in the list
3. Assign the adjacent node of current node in the list to its previous node.
4. END

Example

Following are the implementations of this operation in various programming languages −

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");

   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void deletenode(int key){
   struct node *temp = head, *prev;
   if (temp != NULL && temp->data == key) {
      head = temp->next;
      return;
   }

   // Find the key to be deleted
   while (temp != NULL && temp->data != key) {
      prev = temp;
      temp = temp->next;
   }

   // If the key is not present
   if (temp == NULL) return;

   // Remove the node
   prev->next = temp->next;
}
void main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(40);
   insertatbegin(55);
   printf("Linked List: ");

   // print list
   printList();
   deletenode(30);
   printf("\nLinked List after deletion: ");

   // print list
   printList();
}

Output

Linked List: 
[ 55  40  30  22  12 ]
Linked List after deletion: 
[ 55  40  22  12 ]
#include <bits/stdc++.h>
#include <string>
using namespace std;
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   cout << "\n[";

   //start from the beginning
   while(p != NULL) {
      cout << " " << p->data << " ";
      p = p->next;
   }
   cout << "]";
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void deletenode(int key){
   struct node *temp = head, *prev;
   if (temp != NULL && temp->data == key) {
      head = temp->next;
      return;
   }

   // Find the key to be deleted
   while (temp != NULL && temp->data != key) {
      prev = temp;
      temp = temp->next;
   }

   // If the key is not present
   if (temp == NULL) return;

   // Remove the node
   prev->next = temp->next;
}
int main(){
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(44);
   insertatbegin(50);
   cout << "Linked List: ";

   // print list
   printList();
   deletenode(30);
   cout << "Linked List after deletion: ";
   printList();
}      

Output

Linked List: 
[ 50  44  30  22  12 ]Linked List after deletion: 
[ 50  44  22  12 ]
public class Linked_List {
   static class node {
      int data;
      node next;
      node (int value) {
         data = value;
         next = null;
      }
   }
   static node head;
   
   // display the list
   static void printList() {
      node p = head;
      System.out.print("\n[");
   
      //start from the beginning
      while(p != null) {
         System.out.print(" " + p.data + " ");
         p = p.next;
      }
      System.out.print("]");
   }
   
   //insertion at the beginning
   static void insertatbegin(int data) {

   
      //create a link
      node lk = new node(data);;

      // point it to old first node
      lk.next = head;

      //point first to new first node
      head = lk;
   }
   static void deletenode(int key) {
      node temp = head;
      node prev = null;
      if (temp != null && temp.data == key) {
         head = temp.next;
         return;
      }
      
      // Find the key to be deleted
      while (temp != null && temp.data != key) {
         prev = temp;
         temp = temp.next;
      }
      
      // If the key is not present
      if (temp == null) return;
      
      // Remove the node
      prev.next = temp.next;
   }
   public static void main(String args[]) {
      int k=0;
      insertatbegin(12);
      insertatbegin(22);
      insertatbegin(30);
      insertatbegin(44);
      insertatbegin(50);
      insertatbegin(33);
      System.out.println("Linked List: ");

      // print list
      printList();

      //deleteatbegin();
      //deleteatend();
      deletenode(12);
      System.out.println("\nLinked List after deletion: ");

      // print list
      printList();
   }
}

Output

Linked List: 

[ 33  50  44  30  22  12 ]
Linked List after deletion: 

[ 33  50  44  30  22 ]
#python code for deletion at given position using linked list.
class Node:
    def __init__(self, data=None):
        self.data = data
        self.next = None
class LinkedList:
    def __init__(self):
        self.head = None
    # display the list
    def printList(self):
        p = self.head
        print("\n[", end="")
        #start from the beginning
        while(p != None):
            print(" ", p.data, " ", end="")
            p = p.next
        print("]")
    #insertion at the beginning
    def insertatbegin(self, data):
        #create a link
        lk = Node(data)
        # point it to old first node
        lk.next = self.head
        #point first to new first node
        self.head = lk
    def deletenode(self, key):
        temp = self.head
        if (temp != None and temp.data == key):
            self.head = temp.next
            return
        # Find the key to be deleted
        while (temp != None and temp.data != key):
            prev = temp
            temp = temp.next
        # If the key is not present
        if (temp == None):
            return
        # Remove the node
        prev.next = temp.next
llist = LinkedList()
llist.insertatbegin(12)
llist.insertatbegin(22)
llist.insertatbegin(30)
llist.insertatbegin(40)
llist.insertatbegin(55)
print("Original Linked List: ", end="")
# print list
llist.printList()
llist.deletenode(30)
print("\nLinked List after deletion: ", end="")
# print list
llist.printList()

Output

Linked List: 
[ 55  40  30  22  12 ]
Linked List after deletion: 
[ 55  40  22  12 ]

Reverse Operation

This operation is a thorough one. We need to make the last node to be pointed by the head node and reverse the whole linked list.

Reverse Operation

First, we traverse to the end of the list. It should be pointing to NULL. Now, we shall make it point to its previous node −

traverse to the end

We have to make sure that the last node is not the last node. So we'll have some temp node, which looks like the head node pointing to the last node. Now, we shall make all left side nodes point to their previous nodes one by one.

temp node

Except the node (first node) pointed by the head node, all nodes should point to their predecessor, making them their new successor. The first node will point to NULL.

point to null

We'll make the head node point to the new first node by using the temp node.

the temp node

Algorithm

Step by step process to reverse a linked list is as follows −

1 START
2. We use three pointers to perform the reversing: prev, next, head.
3. Point the current node to head and assign its next value to the prev node.
4. Iteratively repeat the step 3 for all the nodes in the list.
5. Assign head to the prev node.

Example

Following are the implementations of this operation in various programming languages −

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");
   
   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void reverseList(struct node** head){
   struct node *prev = NULL, *cur=*head, *tmp;
   while(cur!= NULL) {
      tmp = cur->next;
      cur->next = prev;
      prev = cur;
      cur = tmp;
   }
   *head = prev;
}
void main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(40);
   insertatbegin(55);
   printf("Linked List: ");

   // print list
   printList();
   reverseList(&head);
   printf("\nReversed Linked List: ");
   printList();
}

Output

Linked List: 
[ 55  40  30  22  12 ]
Reversed Linked List: 
[ 12  22  30  40  55 ]
#include <bits/stdc++.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");

   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void reverseList(struct node** head){
   struct node *prev = NULL, *cur=*head, *tmp;
   while(cur!= NULL) {
      tmp = cur->next;
      cur->next = prev;
      prev = cur;
      cur = tmp;
   }
   *head = prev;
}
int main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(40);
   insertatbegin(55);
   printf("Linked List: ");

   // print list
   printList();
   reverseList(&head);
   printf("\nReversed Linked List: ");
   printList();
   return 0;
}

Output

Linked List: 
[ 55  40  30  22  12 ]
Reversed Linked List: 
[ 12  22  30  40  55 ]
public class Linked_List {
   static Node head;
   static class Node {
      int data;
      Node next;
      Node (int value) {
         data = value;
         next = null;
      }
   }

   // display the list
   static void printList(Node node) {
      System.out.print("\n[");

      //start from the beginning
      while(node != null) {
         System.out.print(" " + node.data + " ");
         node = node.next;
      }
      System.out.print("]");
   }
   static Node reverseList(Node head) {
      Node prev = null;
      Node cur = head;
      Node temp = null;
      while (cur != null) {
         temp = cur.next;
         cur.next = prev;
         prev = cur;
         cur = temp;
      }
      head = prev;
      return head;
   }
   public static void main(String args[]) {
      Linked_List list = new Linked_List();
      list.head = new Node(33);
      list.head.next = new Node(50);
      list.head.next.next = new Node(44);
      list.head.next.next.next = new Node(22);
      list.head.next.next.next.next = new Node(12);
      System.out.println("Linked List: ");
      
      // print list
      list.printList(head);
      head = list.reverseList(head);
      System.out.println("\nReversed linked list ");
      list.printList(head);
   }
}

Output

Linked List: 
[ 33  50  44  22  12 ]
Reversed linked list 

[ 12 22  44  50  33 ]
class Node:
   def __init__(self, data=None):
      self.data = data
      self.next = None

class SLL:
   def __init__(self):
      self.head = None

# Print the linked list
   def listprint(self):
      printval = self.head
      print("Linked List: ")
      while printval is not None:
         print (printval.data)
         printval = printval.next
   def reverse(self):
      prev = None
      curr = self.head
      while(curr is not None):
         next = curr.next
         curr.next = prev
         prev = curr
         curr = next
      self.head = prev

l1 = SLL()
l1.head = Node("731")
e2 = Node("672")
e3 = Node("63")

l1.head.next = e2
e2.next = e3

l1.listprint()
l1.reverse()
print("After reversing: ")
l1.listprint()

Output

Linked List: 
731
672
63
After reversing: 
Linked List: 
63
672
731

Search Operation

Searching for an element in the list using a key element. This operation is done in the same way as array search; comparing every element in the list with the key element given.

Algorithm

1 START
2 If the list is not empty, iteratively check if the list contains the key
3 If the key element is not present in the list, unsuccessful search
4 END

Example

Following are the implementations of this operation in various programming languages −

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");

   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
int searchlist(int key){
   struct node *temp = head;
   while(temp != NULL) {
      if (temp->data == key) {
         return 1;
      }
      temp=temp->next;
   }
   return 0;
}
void main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(40);
   insertatbegin(55);
   printf("Linked List: ");

   // print list
   printList();
   k = searchlist(30);
   if (k == 1)
      printf("\nElement is found");
   else
      printf("\nElement is not present in the list");
}

Output

Linked List: 
[ 55  40  30  22  12 ]
Element is found
#include <bits/stdc++.h>
#include <string>
using namespace std;
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   cout << "\n[";

   //start from the beginning
   while(p != NULL) {
      cout << " " << p->data << " ";
      p = p->next;
   }
   cout << "]";
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
int searchlist(int key){
   struct node *temp = head;
   while(temp != NULL) {
      if (temp->data == key) {
         return 1;
      }
      temp=temp->next;
   }
   return 0;
}
int main(){
   int k = 0;
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(44);
   insertatbegin(50);
   cout << "Linked List: ";

   // print list
   printList();
   k = searchlist(16);
   if (k == 1)
      cout << "\nElement is found";
   else
      cout << "\nElement is not present in the list";
}

Output

Linked List: 
[ 50  44  30  22  12 ]
Element is not present in the list
public class Linked_List {
   static class node {
      int data;
      node next;
      node (int value) {
         data = value;
         next = null;
      }
   }
   static node head;

   // display the list
   static void printList() {
      node p = head;
      System.out.print("\n[");

      //start from the beginning
      while(p != null) {
         System.out.print(" " + p.data + " ");
         p = p.next;
      }
      System.out.print("]");
   }

   //insertion at the beginning
   static void insertatbegin(int data) {

      //create a link
      node lk = new node(data);;

      // point it to old first node
      lk.next = head;
      
      //point first to new first node
      head = lk;
   }
   static int searchlist(int key) {
      node temp = head;
      while(temp != null) {
         if (temp.data == key) {
            return 1;
         }
         temp=temp.next;
      }
      return 0;
   }
   public static void main(String args[]) {
      int k=0;
      insertatbegin(12);
      insertatbegin(22);
      insertatbegin(30);
      insertatbegin(44);
      insertatbegin(50);
      insertatbegin(33);
      System.out.println("Linked List: ");

      // print list
      printList();
      k = searchlist(44);
      if (k == 1)
         System.out.println("\nElement is found");
      else
         System.out.println("\nElement is not present in the list");
   }
}

Output

Linked List: 

[33  50  44  30  22  12 ]
Element is found
class Node:
   def __init__(self, data=None):
      self.data = data
      self.next = None

class SLL:
   def __init__(self):
      self.head = None
   def search(self, x):
      count = 0
      
      # Initialize current to head
      current = self.head

      # loop till current not equal to None
      while current != None:
         if current.data == x:
            print("data found")
            count = count + 1
         current = current.next
      if count == 0:
         print("Data Not found")

l1 = SLL()
l1.head = Node("731")
e2 = Node("672")
e3 = Node("63")

l1.head.next = e2
e2.next = e3

l1.search("63")

Output

data found

Traversal Operation

The traversal operation walks through all the elements of the list in an order and displays the elements in that order.

Algorithm

1. START
2. While the list is not empty and did not reach the end of the list, print the data in each node
3. END

Example

Following are the implementations of this operation in various programming languages −

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

   // display the list
   void printList(){
   struct node *p = head;
   printf("\n[");

   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}

   //insertion at the beginning
   void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   printf("Linked List: ");

   // print list
   printList();
}

Output

Linked List: 
[ 30  22  12 ]
#include <bits/stdc++.h>
#include <string>
using namespace std;
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// Displaying the list
void printList(){
   struct node *p = head;
   while(p != NULL) {
      cout << " " << p->data << " ";
      p = p->next;
   }
}

// Insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
int main(){
   insertatbegin(12);
   insertatbegin(22);
   insertatbegin(30);
   insertatbegin(44);
   insertatbegin(50);
   cout << "Linked List: ";

   // print list
   printList();
}      

Output

Linked List:  50  44  30  22  12 
public class Linked_List {
   static class node {
      int data;
      node next;
      node (int value) {
         data = value;
         next = null;
      }
   }
   static node head;

   // display the list
   static void printList() {
      node p = head;
      System.out.print("\n[");
      
      //start from the beginning
      while(p != null) {
         System.out.print(" " + p.data + " ");
         p = p.next;
      }
      System.out.print("]");
   }
   
   //insertion at the beginning
   static void insertatbegin(int data) {

      //create a link
      node lk = new node(data);;

      // point it to old first node
      lk.next = head;

      //point first to new first node
      head = lk;
   }
   public static void main(String args[]) {
      int k=0;
      insertatbegin(12);
      insertatbegin(22);
      insertatbegin(30);
      insertatbegin(44);
      insertatbegin(50);
      insertatbegin(33);
      System.out.println("Linked List: ");

      // print list
      printList();
   }
}      

Output

Linked List: 
[ 33  50  44  30  22  12 ]
class Node:
   def __init__(self, data=None):
      self.data = data
      self.next = None
class SLL:
   def __init__(self):
      self.head = None

# Print the linked list
   def listprint(self):
      printval = self.head
      print("Linked List: ")
      while printval is not None:
         print (printval.data)
         printval = printval.next

l1 = SLL()
l1.head = Node("731")
e2 = Node("672")
e3 = Node("63")

l1.head.next = e2
e2.next = e3

l1.listprint()      

Output

Linked List: 
731
672
63

Complete implementation

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   printf("\n[");
   //start from the beginning
   while(p != NULL) {
      printf(" %d ",p->data);
      p = p->next;
   }
   printf("]");
}
//insertion at the beginning
void insertatbegin(int data){
   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   // point it to old first node
   lk->next = head;
   //point first to new first node
   head = lk;
}
void insertatend(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   struct node *linkedlist = head;

   // point it to old first node
   while(linkedlist->next != NULL)
      linkedlist = linkedlist->next;

   //point first to new first node
   linkedlist->next = lk;
}
void insertafternode(struct node *list, int data){
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   lk->next = list->next;
   list->next = lk;
}
void deleteatbegin(){
   head = head->next;
}
void deleteatend(){
   struct node *linkedlist = head;
   while (linkedlist->next->next != NULL)
      linkedlist = linkedlist->next;
   linkedlist->next = NULL;
}
void deletenode(int key){
   struct node *temp = head, *prev;
   if (temp != NULL && temp->data == key) {
      head = temp->next;
      return;
   }

   // Find the key to be deleted
   while (temp != NULL && temp->data != key) {
      prev = temp;
      temp = temp->next;
   }

   // If the key is not present
   if (temp == NULL) return;

   // Remove the node
   prev->next = temp->next;
}
int searchlist(int key){
   struct node *temp = head;
   while(temp != NULL) {
      if (temp->data == key) {
         return 1;
      }
      temp=temp->next;
   }
   return 0;
}
void main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatend(30);
   insertatend(44);
   insertatbegin(50);
   insertafternode(head->next->next, 33);
   printf("Linked List: ");

   // print list
   printList();
   deleteatbegin();
   deleteatend();
   deletenode(12);
   printf("\nLinked List after deletion: ");

   // print list
   printList();
   insertatbegin(4);
   insertatbegin(16);
   printf("\nUpdated Linked List: ");
   printList();
   k = searchlist(16);
   if (k == 1)
      printf("\nElement is found");
   else
      printf("\nElement is not present in the list");
}

Output

Linked List: 
[ 50  22  12  33  30  44 ]
Linked List after deletion: 
[ 22  33  30 ]
Updated Linked List: 
[ 16  4  22  33  30 ]
Element is found
#include <bits/stdc++.h>
#include <string>
using namespace std;
struct node {
   int data;
   struct node *next;
};
struct node *head = NULL;
struct node *current = NULL;

// display the list
void printList(){
   struct node *p = head;
   cout << "\n[";

   //start from the beginning
   while(p != NULL) {
      cout << " " << p->data << " ";
      p = p->next;
   }
   cout << "]";
}

//insertion at the beginning
void insertatbegin(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;

   // point it to old first node
   lk->next = head;

   //point first to new first node
   head = lk;
}
void insertatend(int data){

   //create a link
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   struct node *linkedlist = head;

   // point it to old first node
   while(linkedlist->next != NULL)
      linkedlist = linkedlist->next;

   //point first to new first node
   linkedlist->next = lk;
}
void insertafternode(struct node *list, int data){
   struct node *lk = (struct node*) malloc(sizeof(struct node));
   lk->data = data;
   lk->next = list->next;
   list->next = lk;
}
void deleteatbegin(){
   head = head->next;
}
void deleteatend(){
   struct node *linkedlist = head;
   while (linkedlist->next->next != NULL)
      linkedlist = linkedlist->next;
   linkedlist->next = NULL;
}
void deletenode(int key){
   struct node *temp = head, *prev;
   if (temp != NULL && temp->data == key) {
      head = temp->next;
      return;
   }

   // Find the key to be deleted
   while (temp != NULL && temp->data != key) {
      prev = temp;
      temp = temp->next;
   }

   // If the key is not present
   if (temp == NULL) return;

   // Remove the node
   prev->next = temp->next;
}
int searchlist(int key){
   struct node *temp = head;
   while(temp != NULL) {
      if (temp->data == key) {
         temp=temp->next;
         return 1;
      } else
         return 0;
   }
}
int main(){
   int k=0;
   insertatbegin(12);
   insertatbegin(22);
   insertatend(30);
   insertatend(44);
   insertatbegin(50);
   insertafternode(head->next->next, 33);
   cout << "Linked List: ";

   // print list
   printList();
   deleteatbegin();
   deleteatend();
   deletenode(12);
   cout << "\nLinked List after deletion: ";

   // print list
   printList();
   insertatbegin(4);
   insertatbegin(16);
   cout << "\nUpdated Linked List: ";
   printList();
   k = searchlist(16);
   if (k == 1)
      cout << "\nElement is found";
   else
      cout << "\nElement is not present in the list";
   return 0;
}

Output

Linked List: 
[ 50  22  12  33  30  44 ]
Linked List after deletion: 
[ 22  33  30 ]
Updated Linked List: 
[ 16  4  22  33  30 ]
Element is found
public class Linked_List {
   static class node {
      int data;
      node next;
      node (int value) {
         data = value;
         next = null;
      }
   }
   static node head;

   // display the list
   static void printList() {
      node p = head;
      System.out.print("\n[");

      //start from the beginning
      while(p != null) {
         System.out.print(" " + p.data + " ");
         p = p.next;
      }
      System.out.print("]");
   }

   //insertion at the beginning
   static void insertatbegin(int data) {

      //create a link
      node lk = new node(data);;

      // point it to old first node
      lk.next = head;

      //point first to new first node
      head = lk;
   }
   static void insertatend(int data) {

      //create a link
      node lk = new node(data);
      node linkedlist = head;

      // point it to old first node
      while(linkedlist.next != null)
         linkedlist = linkedlist.next;

      //point first to new first node
      linkedlist.next = lk;
   }
   static void insertafternode(node list, int data) {
      node lk = new node(data);
      lk.next = list.next;
      list.next = lk;
   }
   static void deleteatbegin() {
      head = head.next;
   }
   static void deleteatend() {
      node linkedlist = head;
      while (linkedlist.next.next != null)
         linkedlist = linkedlist.next;
      linkedlist.next = null;
   }
   static void deletenode(int key) {
      node temp = head;
      node prev = null;
      if (temp != null && temp.data == key) {
         head = temp.next;
         return;
      }

      // Find the key to be deleted
      while (temp != null && temp.data != key) {
         prev = temp;
         temp = temp.next;
      }
      
      // If the key is not present
      if (temp == null) return;
      
      // Remove the node
      prev.next = temp.next;
   }
   static int searchlist(int key) {
      node temp = head;
      while(temp != null) {
         if (temp.data == key) {
            temp=temp.next;
            return 1;
         }
      }
      return 0;
   }
   public static void main(String args[]) {
      int k=0;
      insertatbegin(12);
      insertatbegin(22);
      insertatend(30);
      insertatend(44);
      insertatbegin(50);
      insertafternode(head.next.next, 33);
      System.out.println("Linked List: ");
      
      // print list
      printList();
      deleteatbegin();
      deleteatend();
      deletenode(12);
      System.out.println("\nLinked List after deletion: ");

      // print list
      printList();
      insertatbegin(4);
      insertatbegin(16);
      System.out.println("\nUpdated Linked List: ");
      printList();
      k = searchlist(16);
      if (k == 1)
         System.out.println("\nElement is found");
      else
         System.out.println("\nElement is not present in the list");
   }
}

Output

Linked List:
[ 50 22 12 33 30 44 ]
Linked List after deletion:
[ 22 33 30 ]
Updated Linked List:
[ 16 4 22 33 30 ]
Element is found
class LLNode:
   def __init__(self, data=None):
      self.data = data
      self.next = None
class LL:
   def __init__(self):
      self.head = None
   def listprint(self):
      printval = self.head
      while printval is not None:
         print(printval.data)
         printval = printval.next
   def AddAtBeginning(self,newdata):
      NewNode = LLNode(newdata)

      # Update the new nodes next val to existing node
      NewNode.next = self.head
      self.head = NewNode

   # Function to add node at a position
   def InsertAtPos(self,nodeatpos,newdata):
      if nodeatpos is None:
         print("The mentioned node is absent")
         return
      NewNode = LLNode(newdata)
      NewNode.next = nodeatpos.next
      nodeatpos.next = NewNode
   def reverse(self):
      prev = None
      curr = self.head
      while(curr is not None):
         next = curr.next
         curr.next = prev
         prev = curr
         curr = next
      self.head = prev
   def search(self, x):
      count = 0

      # Initialize current to head
      current = self.head

      # loop till current not equal to None
      while current != None:
         if current.data == x:
            print("data found")
            count = count + 1
         current = current.next
      if count == 0:
         print("Data Not found")

l1 = LL()
l1.head = LLNode("23")
l2 = LLNode("12")
l3 = LLNode("7")
l4 = LLNode("14")
l5 = LLNode("61")

# Linking the first Node to second node
l1.head.next = l2

# Linking the second Node to third node
l2.next = l3
l3.next = l4
l4.next = l5
print("Original Linked List: ")
l1.listprint()

l1.AddAtBeginning("45")
l1.InsertAtPos(l1.head.next.next, "4")
print("Updated Linked List:")
l1.listprint()
l1.reverse()

print("Reversed Linked List:")
l1.listprint()
l1.search("7")

Output

Original Linked List: 
23
12
7
14
61
Updated Linked List:
45
23
12
4
7
14
61
Reversed Linked List:
61
14
7
4
12
23
45
data found
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