Delete a Doubly Linked List node at a given position in C++

In this tutorial, we are going to learn how to delete a node in doubly linked list with the given position.

Let's see the steps to solve the problem.

• Write struct with data, prev and next pointers.

• Write a function to insert the node into the doubly linked list.

• Initialize the doubly linked list with dummy data.

• Initialize the position to delete the node.

• Iterate over the linked list and find the node with the given position to delete the node.

• Write a function to delete the node. Consider the following three cases while deleting the node.

  • If the node is head node, then move the head to next node.

  • If the node is middle node, then link the next node to the previous node

  • If the node is end node, then remove the previous node link.

Example

Let's see the code.

 Live Demo

#include <bits/stdc++.h>
using namespace std;
struct Node {
   int data;
   struct Node *prev, *next;
};
void deleteNode(struct Node** head_ref, struct Node* del) {
   if (*head_ref == NULL || del == NULL) {
      return;
   }
   // head node
   if (*head_ref == del) {
      *head_ref = del->next;
   }
   // middle node
   if (del->next != NULL) {
      del->next->prev = del->prev;
   }
   // end node
   if (del->prev != NULL) {
      del->prev->next = del->next;
   }
   free(del);
}
void deleteNodeAtGivenPosition(struct Node** head_ref, int n) {
   if (*head_ref == NULL || n <= 0) {
      return;
   }
   struct Node* current = *head_ref;
   int i;
   for (int i = 1; current != NULL && i < n; i++) {
      current = current->next;
   }
   if (current == NULL) {
      return;
   }
   deleteNode(head_ref, current);
}
void insertNode(struct Node** head_ref, int new_data) {
   struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
   new_node->data = new_data;
   new_node->prev = NULL;
   new_node->next = (*head_ref);
   if ((*head_ref) != NULL) {
      (*head_ref)->prev = new_node;
   }
   (*head_ref) = new_node;
}
void printLinkedList(struct Node* head) {
   while (head != NULL) {
      cout << head->data << "->";
      head = head->next;
   }
}
int main() {
   struct Node* head = NULL;
   insertNode(&head, 5);
   insertNode(&head, 2);
   insertNode(&head, 4);
   insertNode(&head, 8);
   insertNode(&head, 10);
   cout << "Doubly linked list before deletion" << endl;
   printLinkedList(head);
   int n = 2;
   deleteNodeAtGivenPosition(&head, n);
   cout << "\nDoubly linked list after deletion" << endl;
   printLinkedList(head);
   return 0;
}

Output

If you execute the above program, then you will get the following result.

Doubly linked list before deletion
10->8->4->2->5->
Doubly linked list after deletion
10->4->2->5->

Conclusion

If you have any queries in the tutorial, mention them in the comment section.

Hafeezul Kareem

Published on 30-Dec-2020 06:38:22

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