Delete all occurrences of a given key in a linked list
Given a singly linked list, delete all occurrences of a given key in it. For example, consider the following list.
Example:
Input: 2 -> 2 -> 1 -> 8 -> 2 -> 3 -> 2 -> 7
Key to delete = 2
Output: 1 -> 8 -> 3 -> 7
This is mainly an extension of this post which deletes the first occurrence of a given key.
We need to first check for all occurrences at the head node and change the head node appropriately. Then we need to check for all occurrences inside a loop and delete them one by one.
Below is the implementation of the above idea:
C++
// C++ program to delete all occurrences// of a given key in linked list#include <bits/stdc++.h>using namespace std;// A linked list nodeclass Node{ public: int data; Node* next;};// Given a reference (pointer) to the head// of a list and an int, inserts a new node// on the front of the listNode* push(Node* head, int new_data){ Node* new_node = new Node(); new_node->data = new_data; new_node->next = head; head = new_node; return head;}// Given a reference (pointer)to the head// of a list and a key, deletes all// occurrence of the given key in// linked listNode* deleteKey(Node *head,int x){ // Store head node Node *tmp = head; while (head->data == x) { head = head->next; } while (tmp->next != NULL) { if (tmp->next->data == x) { tmp->next = tmp->next->next; } else { tmp = tmp->next; } } return head;}// This function prints contents of// linked list starting from the// given nodevoid printList(Node* node){ while (node->next != NULL) { cout << node->data << " "; node = node->next; } cout << node->data;} // Driver codeint main(){ // Start with the empty list Node* head = NULL; head = push(head, 7); head = push(head, 2); head = push(head, 3); head = push(head, 2); head = push(head, 8); head = push(head, 1); head = push(head, 2); head = push(head, 2); // Key to delete int key = 2 ; cout << "Created Linked List:\n "; printList(head); // Function call head = deleteKey(head, key); cout << "\nLinked List after Deletion is:\n"; printList(head); return 0;}// This code is contributed by shivamsharma2020 |
C
// C Program to delete all occurrences of a given key in// linked list#include <stdio.h>#include <stdlib.h>// A linked list nodestruct Node{ int data; struct Node* next;};/* Given a reference (pointer to pointer) to the head of a list and an int, inserts a new node on the front of the list. */void push(struct Node** head_ref, int new_data){ struct Node* new_node = (struct Node*)malloc(sizeof(struct Node)); new_node->data = new_data; new_node->next = (*head_ref); (*head_ref) = new_node;}/* Given a reference (pointer to pointer) to the head of a list and a key, deletes all occurrence of the given key in linked list */void deleteKey(struct Node** head_ref, int key){ // Store head node struct Node *temp = *head_ref, *prev; // If head node itself holds the key or multiple // occurrences of key while (temp != NULL && temp->data == key) { *head_ref = temp->next; // Changed head free(temp); // free old head temp = *head_ref; // Change Temp } // Delete occurrences other than head while (temp != NULL) { // Search for the key to be deleted, keep track of // the previous node as we need to change // 'prev->next' while (temp != NULL && temp->data != key) { prev = temp; temp = temp->next; } // If key was not present in linked list if (temp == NULL) return; // Unlink the node from linked list prev->next = temp->next; free(temp); // Free memory // Update Temp for next iteration of outer loop temp = prev->next; }}// This function prints contents of linked list starting// from the given nodevoid printList(struct Node* node){ while (node != NULL) { printf(" %d ", node->data); node = node->next; }}// Driver codeint main(){ // Start with the empty list struct Node* head = NULL; push(&head, 7); push(&head, 2); push(&head, 3); push(&head, 2); push(&head, 8); push(&head, 1); push(&head, 2); push(&head, 2); int key = 2; // key to delete puts("Created Linked List: "); printList(head); // Function call deleteKey(&head, key); puts("\nLinked List after Deletion is:"); printList(head); return 0;} |
Java
// Java Program to delete all occurrences// of a given key in linked listclass LinkedList{ static Node head; // head of list /* Linked list Node*/ class Node { int data; Node next; Node(int d) { data = d; next = null; } } /* Given a key, deletes all occurrence of the given key in linked list */ void deleteKey(int key) { // Store head node Node temp = head, prev = null; // If head node itself holds the key // or multiple occurrences of key while (temp != null && temp.data == key) { head = temp.next; // Changed head temp = head; // Change Temp } // Delete occurrences other than head while (temp != null) { // Search for the key to be deleted, // keep track of the previous node // as we need to change 'prev->next' while (temp != null && temp.data != key) { prev = temp; temp = temp.next; } // If key was not present in linked list if (temp == null) return; // Unlink the node from linked list prev.next = temp.next; // Update Temp for next iteration of outer loop temp = prev.next; } } /* Inserts a new Node at front of the list. */ public void push(int new_data) { Node new_node = new Node(new_data); new_node.next = head; head = new_node; } /* This function prints contents of linked list starting from the given node */ public void printList() { Node tnode = head; while (tnode != null) { System.out.print(tnode.data + " "); tnode = tnode.next; } } // Driver Code public static void main(String[] args) { LinkedList llist = new LinkedList(); llist.push(7); llist.push(2); llist.push(3); llist.push(2); llist.push(8); llist.push(1); llist.push(2); llist.push(2); int key = 2; // key to delete System.out.println("Created Linked list is:"); llist.printList(); // Function call llist.deleteKey(key); System.out.println( "\nLinked List after Deletion is:"); llist.printList(); }}// This code is contributed by Shubham |
Python3
# Python3 program to delete all occurrences# of a given key in linked list# Link list nodeclass Node: def __init__(self, data): self.data = data self.next = None# Given a reference (pointer to pointer)# to the head of a list and an int,# inserts a new node on the front of the list.def push(head_ref, new_data): new_node = Node(0) new_node.data = new_data new_node.next = (head_ref) (head_ref) = new_node return head_ref# Given a reference (pointer to pointer)# to the head of a list and a key,# deletes all occurrence of the given key# in linked listdef deleteKey(head_ref, key): # Store head node temp = head_ref prev = None # If head node itself holds the key # or multiple occurrences of key while (temp != None and temp.data == key): head_ref = temp.next # Changed head temp = head_ref # Change Temp # Delete occurrences other than head while (temp != None): # Search for the key to be deleted, # keep track of the previous node # as we need to change 'prev.next' while (temp != None and temp.data != key): prev = temp temp = temp.next # If key was not present in linked list if (temp == None): return head_ref # Unlink the node from linked list prev.next = temp.next # Update Temp for next iteration of outer loop temp = prev.next return head_ref# This function prints contents of linked list# starting from the given nodedef printList(node): while (node != None): print(node.data, end=" ") node = node.next# Driver Codeif __name__ == '__main__': # Start with the empty list head = None head = push(head, 7) head = push(head, 2) head = push(head, 3) head = push(head, 2) head = push(head, 8) head = push(head, 1) head = push(head, 2) head = push(head, 2) key = 2 # key to delete print("Created Linked List: ") printList(head) # Function call head = deleteKey(head, key) print("\nLinked List after Deletion is: ") printList(head)# This code is contributed by Arnab Kundu |
C#
// C# Program to delete all occurrences// of a given key in linked listusing System;class GFG{ static Node head; // head of list /* Linked list Node*/ public class Node { public int data; public Node next; public Node(int d) { data = d; next = null; } } /* Given a key, deletes all occurrence of the given key in linked list */ void deleteKey(int key) { // Store head node Node temp = head, prev = null; // If head node itself holds the key // or multiple occurrences of key while (temp != null && temp.data == key) { head = temp.next; // Changed head temp = head; // Change Temp } // Delete occurrences other than head while (temp != null) { // Search for the key to be deleted, // keep track of the previous node // as we need to change 'prev->next' while (temp != null && temp.data != key) { prev = temp; temp = temp.next; } // If key was not present in linked list if (temp == null) return; // Unlink the node from linked list prev.next = temp.next; // Update Temp for next iteration of outer loop temp = prev.next; } } /* Inserts a new Node at front of the list. */ public void Push(int new_data) { Node new_node = new Node(new_data); new_node.next = head; head = new_node; } /* This function prints contents of linked list starting from the given node */ public void printList() { Node tnode = head; while (tnode != null) { Console.Write(tnode.data + " "); tnode = tnode.next; } } // Driver Code public static void Main(String[] args) { GFG llist = new GFG(); llist.Push(7); llist.Push(2); llist.Push(3); llist.Push(2); llist.Push(8); llist.Push(1); llist.Push(2); llist.Push(2); int key = 2; // key to delete Console.WriteLine("Created Linked list is:"); llist.printList(); // Function call llist.deleteKey(key); Console.WriteLine( "\nLinked List after Deletion is:"); llist.printList(); }}// This code is contributed by 29AjayKumar |
Output
Created Linked List: 2 2 1 8 2 3 2 7 Linked List after Deletion is: 1 8 3 7
This article is contributed by Saransh. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
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