Delete a node in a Doubly Linked List
Pre-requisite: Doubly Link List Set 1| Introduction and Insertion
Write a function to delete a given node in a doubly-linked list.
Original Doubly Linked List
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Approach: The deletion of a node in a doubly-linked list can be divided into three main categories:
- After the deletion of the head node.
- After the deletion of the middle node.
- After the deletion of the last node.
All three mentioned cases can be handled in two steps if the pointer of the node to be deleted and the head pointer is known.
- If the node to be deleted is the head node then make the next node as head.
- If a node is deleted, connect the next and previous node of the deleted node.
Algorithm
- Let the node to be deleted be del.
- If node to be deleted is head node, then change the head pointer to next current head.
if headnode == del then
headnode = del.nextNode- Set next of previous to del, if previous to del exists.
if del.nextNode != none
del.nextNode.previousNode = del.previousNode - Set prev of next to del, if next to del exists.
if del.previousNode != none
del.previousNode.nextNode = del.nextC++
// C++ program to delete a node from// Doubly Linked List#include <bits/stdc++.h>using namespace std;/* a node of the doubly linked list */class Node{ public: int data; Node* next; Node* prev;};/* Function to delete a node in a Doubly Linked List.head_ref --> pointer to head node pointer.del --> pointer to node to be deleted. */void deleteNode(Node** head_ref, Node* del){ /* base case */ if (*head_ref == NULL || del == NULL) return; /* If node to be deleted is head node */ if (*head_ref == del) *head_ref = del->next; /* Change next only if node to be deleted is NOT the last node */ if (del->next != NULL) del->next->prev = del->prev; /* Change prev only if node to be deleted is NOT the first node */ if (del->prev != NULL) del->prev->next = del->next; /* Finally, free the memory occupied by del*/ free(del); return;}/* UTILITY FUNCTIONS *//* Function to insert a node at thebeginning of the Doubly Linked List */void push(Node** head_ref, int new_data){ /* allocate node */ Node* new_node = new Node(); /* put in the data */ new_node->data = new_data; /* since we are adding at the beginning, prev is always NULL */ new_node->prev = NULL; /* link the old list off the new node */ new_node->next = (*head_ref); /* change prev of head node to new node */ if ((*head_ref) != NULL) (*head_ref)->prev = new_node; /* move the head to point to the new node */ (*head_ref) = new_node;}/* Function to print nodes in a given doubly linked listThis function is same as printList() of singly linked list */void printList(Node* node){ while (node != NULL) { cout << node->data << " "; node = node->next; }}/* Driver code*/int main(){ /* Start with the empty list */ Node* head = NULL; /* Let us create the doubly linked list 10<->8<->4<->2 */ push(&head, 2); push(&head, 4); push(&head, 8); push(&head, 10); cout << "Original Linked list "; printList(head); /* delete nodes from the doubly linked list */ deleteNode(&head, head); /*delete first node*/ deleteNode(&head, head->next); /*delete middle node*/ deleteNode(&head, head->next); /*delete last node*/ /* Modified linked list will be NULL<-8->NULL */ cout << "\nModified Linked list "; printList(head); return 0;}// This code is contributed by rathbhupendra |
C
#include <stdio.h>#include <stdlib.h>/* a node of the doubly linked list */struct Node { int data; struct Node* next; struct Node* prev;};/* Function to delete a node in a Doubly Linked List. head_ref --> pointer to head node pointer. del --> pointer to node to be deleted. */void deleteNode(struct Node** head_ref, struct Node* del){ /* base case */ if (*head_ref == NULL || del == NULL) return; /* If node to be deleted is head node */ if (*head_ref == del) *head_ref = del->next; /* Change next only if node to be deleted is NOT the last node */ if (del->next != NULL) del->next->prev = del->prev; /* Change prev only if node to be deleted is NOT the first node */ if (del->prev != NULL) del->prev->next = del->next; /* Finally, free the memory occupied by del*/ free(del); return;}/* UTILITY FUNCTIONS *//* Function to insert a node at the beginning of the Doubly Linked List */void push(struct Node** head_ref, int new_data){ /* allocate node */ struct Node* new_node = (struct Node*)malloc(sizeof(struct Node)); /* put in the data */ new_node->data = new_data; /* since we are adding at the beginning, prev is always NULL */ new_node->prev = NULL; /* link the old list off the new node */ new_node->next = (*head_ref); /* change prev of head node to new node */ if ((*head_ref) != NULL) (*head_ref)->prev = new_node; /* move the head to point to the new node */ (*head_ref) = new_node;}/* Function to print nodes in a given doubly linked list This function is same as printList() of singly linked list */void printList(struct Node* node){ while (node != NULL) { printf("%d ", node->data); node = node->next; }}/* Driver program to test above functions*/int main(){ /* Start with the empty list */ struct Node* head = NULL; /* Let us create the doubly linked list 10<->8<->4<->2 */ push(&head, 2); push(&head, 4); push(&head, 8); push(&head, 10); printf("\n Original Linked list "); printList(head); /* delete nodes from the doubly linked list */ deleteNode(&head, head); /*delete first node*/ deleteNode(&head, head->next); /*delete middle node*/ deleteNode(&head, head->next); /*delete last node*/ /* Modified linked list will be NULL<-8->NULL */ printf("\n Modified Linked list "); printList(head); getchar();} |
Java
// Java program to delete a node from// Doubly Linked List// Class for Doubly Linked Listpublic class DLL { Node head; // head of list /* Doubly Linked list Node*/ class Node { int data; Node prev; Node next; // Constructor to create a new node // next and prev is by default initialized // as null Node(int d) { data = d; } } // Adding a node at the front of the list public void push(int new_data) { // 1. allocate node // 2. put in the data Node new_Node = new Node(new_data); // 3. Make next of new node as head // and previous as NULL new_Node.next = head; new_Node.prev = null; // 4. change prev of head node to new node if (head != null) head.prev = new_Node; // 5. move the head to point to the new node head = new_Node; } // This function prints contents of linked list // starting from the given node public void printlist(Node node) { Node last = null; while (node != null) { System.out.print(node.data + " "); last = node; node = node.next; } System.out.println(); } // Function to delete a node in a Doubly Linked List. // head_ref --> pointer to head node pointer. // del --> data of node to be deleted. void deleteNode(Node del) { // Base case if (head == null || del == null) { return; } // If node to be deleted is head node if (head == del) { head = del.next; } // Change next only if node to be deleted // is NOT the last node if (del.next != null) { del.next.prev = del.prev; } // Change prev only if node to be deleted // is NOT the first node if (del.prev != null) { del.prev.next = del.next; } // Finally, free the memory occupied by del return; } // Driver Code public static void main(String[] args) { // Start with the empty list DLL dll = new DLL(); // Insert 2. So linked list becomes 2->NULL dll.push(2); // Insert 4. So linked list becomes 4->2->NULL dll.push(4); // Insert 8. So linked list becomes 8->4->2->NULL dll.push(8); // Insert 10. So linked list becomes 10->8->4->2->NULL dll.push(10); System.out.print("Created DLL is: "); dll.printlist(dll.head); // Deleting first node dll.deleteNode(dll.head); // List after deleting first node // 8->4->2 System.out.print("\nList after deleting first node: "); dll.printlist(dll.head); // Deleting middle node from 8->4->2 dll.deleteNode(dll.head.next); System.out.print("\nList after Deleting middle node: "); dll.printlist(dll.head); }} |
Python
# Program to delete a node in a doubly-linked list# for Garbage collectionimport gc# A node of the doubly linked listclass Node: # Constructor to create a new node def __init__(self, data): self.data = data self.next = None self.prev = Noneclass DoublyLinkedList: # Constructor for empty Doubly Linked List def __init__(self): self.head = None # Function to delete a node in a Doubly Linked List. # head_ref --> pointer to head node pointer. # dele --> pointer to node to be deleted def deleteNode(self, dele): # Base Case if self.head is None or dele is None: return # If node to be deleted is head node if self.head == dele: self.head = dele.next # Change next only if node to be deleted is NOT # the last node if dele.next is not None: dele.next.prev = dele.prev # Change prev only if node to be deleted is NOT # the first node if dele.prev is not None: dele.prev.next = dele.next # Finally, free the memory occupied by dele # Call python garbage collector gc.collect() # Given a reference to the head of a list and an # integer, inserts a new node on the front of list def push(self, new_data): # 1. Allocates node # 2. Put the data in it new_node = Node(new_data) # 3. Make next of new node as head and # previous as None (already None) new_node.next = self.head # 4. change prev of head node to new_node if self.head is not None: self.head.prev = new_node # 5. move the head to point to the new node self.head = new_node def printList(self, node): while(node is not None): print node.data, node = node.next# Driver program to test the above functions# Start with empty listdll = DoublyLinkedList()# Let us create the doubly linked list 10<->8<->4<->2dll.push(2);dll.push(4);dll.push(8);dll.push(10);print "\n Original Linked List",dll.printList(dll.head)# delete nodes from doubly linked listdll.deleteNode(dll.head)dll.deleteNode(dll.head.next)dll.deleteNode(dll.head.next)# Modified linked list will be NULL<-8->NULLprint "\n Modified Linked List",dll.printList(dll.head)# This code is contributed by Nikhil Kumar Singh(nickzuck_007) |
C#
// C# program to delete a node from// Doubly Linked Listusing System;// Class for Doubly Linked Listpublic class DLL{ Node head; // head of list /* Doubly Linked list Node*/ public class Node { public int data; public Node prev; public Node next; // Constructor to create a new node // next and prev is by default // initialized as null public Node(int d) { data = d; } } // Adding a node at the front of the list public void push(int new_data) { // 1. allocate node // 2. put in the data Node new_Node = new Node(new_data); // 3. Make next of new node as head // and previous as NULL new_Node.next = head; new_Node.prev = null; // 4. change prev of head node to new node if (head != null) head.prev = new_Node; // 5. move the head to point to the new node head = new_Node; } // This function prints contents of linked list // starting from the given node public void printlist(Node node) { while (node != null) { Console.Write(node.data + " "); node = node.next; } Console.WriteLine(); } // Function to delete a node in a Doubly Linked List. // head_ref --> pointer to head node pointer. // del --> data of node to be deleted. void deleteNode(Node del) { // Base case if (head == null || del == null) { return; } // If node to be deleted is head node if (head == del) { head = del.next; } // Change next only if node to be deleted // is NOT the last node if (del.next != null) { del.next.prev = del.prev; } // Change prev only if node to be deleted // is NOT the first node if (del.prev != null) { del.prev.next = del.next; } // Finally, free the memory occupied by del return; } // Driver Code public static void Main() { // Start with the empty list DLL dll = new DLL(); // Insert 2. So linked list becomes 2->NULL dll.push(2); // Insert 4. So linked list becomes 4->2->NULL dll.push(4); // Insert 8. So linked list becomes 8->4->2->NULL dll.push(8); // Insert 10. So linked list becomes 10->8->4->2->NULL dll.push(10); Console.Write("Created DLL is: "); dll.printlist(dll.head); // Deleting first node dll.deleteNode(dll.head); // List after deleting first node // 8->4->2 Console.Write("\nList after deleting first node: "); dll.printlist(dll.head); // Deleting middle node from 8->4->2 dll.deleteNode(dll.head.next); Console.Write("\nList after Deleting middle node: "); dll.printlist(dll.head); }}// This code is contributed by PrinciRaj1992 |
Javascript
<script>// Javascript program to delete a node from// Doubly Linked List// Class for Doubly Linked Listvar head; // head of list /* Doubly Linked list Node */ class Node { // Constructor to create a new node // next and prev is by default initialized // as null constructor(val) { this.data = val; this.prev = null; this.next = null; } } // Adding a node at the front of the list function push(new_data) { // 1. allocate node // 2. put in the data new_Node = new Node(new_data); // 3. Make next of new node as head // and previous as NULL new_Node.next = head; new_Node.prev = null; // 4. change prev of head node to new node if (head != null) head.prev = new_Node; // 5. move the head to point to the new node head = new_Node; } // This function prints contents of linked list // starting from the given node function printlist( node) { last = null; while (node != null) { document.write(node.data + " "); last = node; node = node.next; } document.write("<br/>"); } // Function to delete a node in a Doubly Linked List. // head_ref --> pointer to head node pointer. // del --> data of node to be deleted. function deleteNode( del) { // Base case if (head == null || del == null) { return; } // If node to be deleted is head node if (head == del) { head = del.next; } // Change next only if node to be deleted // is NOT the last node if (del.next != null) { del.next.prev = del.prev; } // Change prev only if node to be deleted // is NOT the first node if (del.prev != null) { del.prev.next = del.next; } // Finally, free the memory occupied by del return; } // Driver Code // Start with the empty list // Insert 2. So linked list becomes 2->NULL push(2); // Insert 4. So linked list becomes 4->2->NULL push(4); // Insert 8. So linked list becomes 8->4->2->NULL push(8); // Insert 10. So linked list becomes 10->8->4->2->NULL push(10); document.write("Created DLL is: "); printlist(head); // Deleting first node deleteNode(head); deleteNode(head.next); deleteNode(head.next); document.write("Modified Linked list: "); printlist(head);// This code is contributed by todaysgaurav</script> |
Output:
Original Linked list 10 8 4 2 Modified Linked list 8
Complexity Analysis:
- Time Complexity: O(1).
Since traversal of the linked list is not required so the time complexity is constant. - Space Complexity: O(1).
As no extra space is required, so the space complexity is constant.
Please write comments if you find any of the above codes/algorithms incorrect, or find better ways to solve the same problem.
