Insert a Node at a specific position in Doubly Linked List

Last Updated : 07 Aug, 2024

Given a Doubly Linked List, the task is to insert a new node at a specific position in the linked list.

Examples:

Input: Linked List = 1 <-> 2 <-> 4, newData = 3, position = 3
Output: Linked List = 1 <-> 2 <-> 3 <-> 4
Explanation: New node with data = 3 is inserted at position 3
Input: Linked List = 2 <-> 3, newData = 1, position = 1
Output: Linked List = 1 <-> 2 <-> 3
Explanation: New node with data = 1 is inserted at position 1

Approach:

The idea is to traverse the linked list to find the node at position - 1, say current node. If the position is valid, create a new node with the given data and update its pointers: Set the next pointer of new node to next of current node and previous pointer of new node to current node. Similarly, update next pointer of current node to the new node and prev pointer of new node’s next to the new node.

Insertion-at-a-Specific-Position-in-Doubly-Linked-List — Insert node 3 at position 3 in Doubly Linked List

To insert a new node at a specific position,

If position = 1, create a new node and make it the head of the linked list and return it.
Otherwise, traverse the list to reach the node at position – 1, say curr.
If the position is valid, create a new node with given data, say new_node.
Update the next pointer of new node to the next of current node and prev pointer of new node to current node, new_node->next = curr->next and new_node->prev = curr.
Similarly, update next pointer of current node to the new node, curr->next = new_node.
If the new node is not the last node, update prev pointer of new node’s next to the new node, new_node->next->prev = new_node.

C++

// C++ Program to insert a node at a given position  #include <bits/stdc++.h> using namespace std;  struct Node {     int data;     Node *next, *prev;      Node(int new_data) {         data = new_data;         next = prev = nullptr;     } };  // Function to insert a new node at a given position Node *insertAtPosition(Node *head, int pos, int new_data) {      // Create a new node     Node *new_node = new Node(new_data);      // Insertion at the beginning     if (pos == 1) {         new_node->next = head;          // If the linked list is not empty, set the prev of head to new node         if (head != NULL)             head->prev = new_node;          // Set the new node as the head of linked list         head = new_node;         return head;     }      Node *curr = head;     // Traverse the list to find the node before the     // insertion point     for (int i = 1; i < pos - 1 && curr != NULL; ++i) {         curr = curr->next;     }      // If the position is out of bounds     if (curr == NULL) {         cout << "Position is out of bounds." << endl;         delete new_node;         return head;     }      // Set the prev of new node to curr     new_node->prev = curr;      // Set the new of new node to next of curr     new_node->next = curr->next;      // Update the next of current node to new node     curr->next = new_node;      // If the new node is not the last node, update prev of next node to new node     if (new_node->next != NULL)         new_node->next->prev = new_node;      // Return the head of the doubly linked list     return head; }  void printList(Node *head) {     Node *curr = head;     while (curr != NULL) {         cout << curr->data << " ";         curr = curr->next;     }     cout << endl; }  int main() {      // Create a harcoded doubly linked list:     // 1 <-> 2 <-> 4     Node *head = new Node(1);     head->next = new Node(2);     head->next->prev = head;     head->next->next = new Node(4);     head->next->next->prev = head->next;      // Print the original list     cout << "Original Linked List: ";     printList(head);      // Insert new node with data 3 at position 3     cout << "Inserting Node with data 3 at position 3: ";     int data = 3;     int pos = 3;     head = insertAtPosition(head, pos, data);      // Print the updated list     printList(head);      return 0; }

// C Program to insert a node at a given position  #include <stdio.h>  struct Node {     int data;     struct Node *next;     struct Node *prev; };  // Function to create a new node with the given data struct Node *createNode(int new_data) {     struct Node *new_node = (struct Node *)malloc(sizeof(struct Node));     new_node->data = new_data;     new_node->next = NULL;     return new_node; }  // Function to insert a new node at a given position struct Node* insertAtPosition(struct Node *head, int pos, int new_data) {     // Create a new node     struct Node *new_node = createNode(new_data);      // Insertion at the beginning     if (pos == 1) {         new_node->next = head;          // If the linked list is not empty, set the prev of head to new node         if (head != NULL) {             head->prev = new_node;         }          // Set the new node as the head of linked list         head = new_node;         return head;     }      struct Node *curr = head;        // Traverse the list to find the node before the insertion point     for (int i = 1; i < pos - 1 && curr != NULL; ++i) {         curr = curr->next;     }      // If the position is out of bounds     if (curr == NULL) {         printf("Position is out of bounds.\n");         free(new_node);         return head;     }      // Set the prev of new node to curr     new_node->prev = curr;      // Set the next of new node to next of curr     new_node->next = curr->next;      // Update the next of current node to new node     curr->next = new_node;      // If the new node is not the last node, update the prev of next node to new node     if (new_node->next != NULL) {         new_node->next->prev = new_node;     }      // Return the head of the doubly linked list     return head; }  // Function to print the linked list void printList(struct Node *head) {     struct Node *curr = head;     while (curr != NULL) {         printf("%d ", curr->data);         curr = curr->next;     }     printf("\n"); }  int main() {        // Create a hardcoded doubly linked list:     // 1 <-> 2 <-> 4     struct Node *head = createNode(1);     head->next = createNode(2);     head->next->prev = head;     head->next->next = createNode(4);     head->next->next->prev = head->next;      // Print the original list     printf("Original Linked List: ");     printList(head);      // Insert new node with data 3 at position 3     printf("Inserting Node with data 3 at position 3: ");     int data = 3;     int pos = 3;     head = insertAtPosition(head, pos, data);      // Print the updated list     printList(head);      return 0; }

Java

// Java Program to insert a node at a given position  class Node {     int data;     Node next;     Node prev;      Node(int new_data) {         data = new_data;         next = prev = null;     } }  public class GFG {      // Function to insert a new node at a given position     public static Node insertAtPosition(Node head, int pos, int new_data) {         // Create a new node         Node new_node = new Node(new_data);          // Insertion at the beginning         if (pos == 1) {             new_node.next = head;              // If the linked list is not empty, set the prev of head to new node             if (head != null) {                 head.prev = new_node;             }              // Set the new node as the head of linked list             head = new_node;             return head;         }          Node curr = head;                // Traverse the list to find the node before the insertion point         for (int i = 1; i < pos - 1 && curr != null; ++i) {             curr = curr.next;         }          // If the position is out of bounds         if (curr == null) {             System.out.println("Position is out of bounds.");             return head;         }          // Set the prev of new node to curr         new_node.prev = curr;          // Set the next of new node to next of curr         new_node.next = curr.next;          // Update the next of current node to new node         curr.next = new_node;          // If the new node is not the last node, update prev of next node to new node         if (new_node.next != null) {             new_node.next.prev = new_node;         }          // Return the head of the doubly linked list         return head;     }      // Function to print the linked list     public static void printList(Node head) {         Node curr = head;         while (curr != null) {             System.out.print(curr.data + " ");             curr = curr.next;         }         System.out.println();     }      public static void main(String[] args) {                // Create a hardcoded doubly linked list:         // 1 <-> 2 <-> 4         Node head = new Node(1);         head.next = new Node(2);         head.next.prev = head;         head.next.next = new Node(4);         head.next.next.prev = head.next;          // Print the original list         System.out.print("Original Linked List: ");         printList(head);          // Insert new node with data 3 at position 3         System.out.print("Inserting Node with data 3 at position 3: ");         int data = 3;         int pos = 3;         head = insertAtPosition(head, pos, data);          // Print the updated list         printList(head);     } }

Python

# Python Program to insert a node at a given position  class Node:     def __init__(self, new_data):         self.data = new_data         self.next = None         self.prev = None  def insert_at_position(head, pos, new_data):        # Create a new node     new_node = Node(new_data)      # Insertion at the beginning     if pos == 1:         new_node.next = head          # If the linked list is not empty, set the prev of head to new node         if head is not None:             head.prev = new_node          # Set the new node as the head of the linked list         head = new_node         return head      curr = head          # Traverse the list to find the node before the insertion point     for _ in range(1, pos - 1):         if curr is None:             print("Position is out of bounds.")             return head         curr = curr.next      # If the position is out of bounds     if curr is None:         print("Position is out of bounds.")         return head      # Set the prev of new node to curr     new_node.prev = curr      # Set the next of new node to next of curr     new_node.next = curr.next      # Update the next of current node to new node     curr.next = new_node      # If the new node is not the last node, update prev of next node to new node     if new_node.next is not None:         new_node.next.prev = new_node      return head  def print_list(head):     curr = head     while curr is not None:         print(curr.data, end=" ")         curr = curr.next     print()  if __name__ == "__main__":        # Create a hardcoded doubly linked list:     # 1 <-> 2 <-> 4     head = Node(1)     head.next = Node(2)     head.next.prev = head     head.next.next = Node(4)     head.next.next.prev = head.next      # Print the original list     print("Original Linked List: ", end="")     print_list(head)      # Insert new node with data 3 at position 3     print("Inserting Node with data 3 at position 3: ", end="")     data = 3     pos = 3     head = insert_at_position(head, pos, data)      # Print the updated list     print_list(head)

// C# Program to insert a node at a given position  using System;  class Node {     public int Data;     public Node Next;     public Node Prev;      public Node(int data) {         Data = data;         Next = null;         Prev = null;     } }  class GFG {        // Function to insert a new node at a given position     static Node InsertAtPosition(Node head, int pos, int newData) {                // Create a new node         Node newNode = new Node(newData);          // Insertion at the beginning         if (pos == 1) {             newNode.Next = head;             if (head != null)                 head.Prev = newNode;             head = newNode;             return head;         }          Node curr = head;                	// Traverse the list to find the node before the insertion point         for (int i = 1; i < pos - 1 && curr != null; ++i) {             curr = curr.Next;         }          // If the position is out of bounds         if (curr == null) {             Console.WriteLine("Position is out of bounds.");             return head;         }          // Set the prev of new node to curr         newNode.Prev = curr;          // Set the next of new node to the next of curr         newNode.Next = curr.Next;          // Update the next of current node to new node         curr.Next = newNode;          // If the new node is not the last node, update prev of next node to new node         if (newNode.Next != null)             newNode.Next.Prev = newNode;          return head;     }      // Function to print the list     static void PrintList(Node head) {         Node curr = head;         while (curr != null) {             Console.Write(curr.Data + " ");             curr = curr.Next;         }         Console.WriteLine();     }      static void Main() {                // Create a hardcoded doubly linked list:         // 1 <-> 2 <-> 4         Node head = new Node(1);         head.Next = new Node(2);         head.Next.Prev = head;         head.Next.Next = new Node(4);         head.Next.Next.Prev = head.Next;          // Print the original list         Console.WriteLine("Original Linked List: ");         PrintList(head);          // Insert new node with data 3 at position 3         Console.WriteLine("Inserting Node with data 3 at position 3: ");         head = InsertAtPosition(head, 3, 3);          // Print the updated list         PrintList(head);     } }

JavaScript

// Javascript Program to insert a node at a given position  class Node {     constructor(data) {         this.data = data;         this.next = null;         this.prev = null;     } }  // Function to insert a new node at a given position function insertAtPosition(head, pos, newData) {      // Create a new node     let newNode = new Node(newData);      // Insertion at the beginning     if (pos === 1) {         newNode.next = head;         if (head !== null) {             head.prev = newNode;         }         head = newNode;         return head;     }      let curr = head;          // Traverse the list to find the node before the insertion point     for (let i = 1; i < pos - 1 && curr !== null; ++i) {         curr = curr.next;     }      // If the position is out of bounds     if (curr === null) {         console.log("Position is out of bounds.");         return head;     }      // Set the prev of new node to curr     newNode.prev = curr;      // Set the next of new node to the next of curr     newNode.next = curr.next;      // Update the next of current node to new node     curr.next = newNode;      // If the new node is not the last node, update prev of next node to new node     if (newNode.next !== null) {         newNode.next.prev = newNode;     }      return head; }  // Function to print the list function printList(head) {     let curr = head;     while (curr !== null) {         console.log(curr.data + " ");         curr = curr.next;     }     console.log(); }  // Create a hardcoded doubly linked list: // 1 <-> 2 <-> 4 let head = new Node(1); head.next = new Node(2); head.next.prev = head; head.next.next = new Node(4); head.next.next.prev = head.next;  // Print the original list console.log("Original Linked List:"); printList(head);  // Insert new node with data 3 at position 3 console.log("Inserting Node with data 3 at position 3:"); head = insertAtPosition(head, 3, 3);  // Print the updated list printList(head);

Output

Original Linked List: 1 2 4  Inserting Node with data 3 at position 3: 1 2 3 4

Time Complexity: O(N), where N is the number of nodes in doubly linked list
Auxiliary Space: O(1)

Insert a node at a specific position in a linked list

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Insert a Node at a specific position in Doubly Linked List

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