Delete all occurrences of a given key in a linked list ?



Delete all occurrences of a given key in a linked list ?

Input:  2 -> 1 -> 8 -> 2 ->  3 ->  2 -> 7
       Key to delete = 2
Output:  1 -> 8 -> 3 -> 7 

Sample Code in C


#include <stdio.h> 
#include <stdlib.h> 
// A linked list node 
struct 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 node 
void printList(struct Node *node) 
{ 
    while (node != NULL) 
    { 
        printf(" %d ", node->data); 
        node = node->next; 
    } 
} 
   /* Drier program to test above functions*/
int 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); 
    deleteKey(&head, key); 
    puts("\nLinked List after Deletion: "); 
    printList(head); 
    return 0; 
}

Output

Created Linked List:
 2  2  1  8  2  3  2  7
Linked List after Deletion:
 1  8  3  7 


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