Delete all the even nodes from a Doubly Linked List in C++

In this tutorial, we are going to learn how to delete all prime nodes from a doubly linked list.

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.

• Iterate over the doubly linked list. Find whether the current node data is even or not.

• If the current data is even, then 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;    Node *prev, *next; }; void insertNode(Node** head_ref, int new_data) {    Node* new_node = (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 deleteNode(Node** head_ref, Node* del) {    if (*head_ref == NULL || del == NULL) {       return;    }    if (*head_ref == del) {       *head_ref = del->next;    }    if (del->next != NULL) {       del->next->prev = del->prev;    }    if (del->prev != NULL) {       del->prev->next = del->next;    }    free(del);    return; } void deleteEvenNodes(Node** head_ref) {    Node* temp = *head_ref;    Node* next;    while (temp != NULL) {       next = temp->next;       if (temp->data % 2 == 0) {          deleteNode(head_ref, temp);       }       temp = next;    } } void printLinkedList(Node* head) {    while (head != NULL) {       cout << head->data << " -> ";       head = head->next;    } } int main() {    Node* head = NULL;    insertNode(&head, 1);    insertNode(&head, 2);    insertNode(&head, 3);    insertNode(&head, 4);    insertNode(&head, 5);    insertNode(&head, 6);    cout << "Linked List before deletion:" << endl;    printLinkedList(head);    deleteEvenNodes(&head);    cout << "\nLinked List after deletion:" << endl;    printLinkedList(head); }

Output

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

Linked List before deletion: 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> Linked List after deletion: 5 -> 3 -> 1 ->

Conclusion

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