C Program For Deleting A Given Node In Linked List Under Given Constraints - GeeksforGeeks

20 Dec, 2021
Given a Singly Linked List, write a function to delete a given node. Your function must follow the following constraints: 
It must accept a pointer to the start node as the first parameter and node to be deleted as the second parameter i.e., a pointer to the head node is not global.It should not return a pointer to the head node.It should not accept pointer to pointer to the head node.
It must accept a pointer to the start node as the first parameter and node to be deleted as the second parameter i.e., a pointer to the head node is not global.
It should not return a pointer to the head node.
It should not accept pointer to pointer to the head node.
You may assume that the Linked List never becomes empty.Let the function name be deleteNode(). In a straightforward implementation, the function needs to modify the head pointer when the node to be deleted is the first node. As discussed in previous post, when a function modifies the head pointer, the function must use one of the given approaches, we can’t use any of those approaches here. Solution We explicitly handle the case when the node to be deleted is the first node, we copy the data of the next node to head and delete the next node. The cases when a deleted node is not the head node can be handled normally by finding the previous node and changing next of the previous node. The following are the implementation.
C
#include <stdio.h>#include <stdlib.h>  // Structure of a linked list // nodestruct Node{    int data;    struct Node *next;};  void deleteNode(struct Node *head,                 struct Node *n){    // When node to be deleted is     // head node    if(head == n)    {        if(head->next == NULL)        {            printf("There is only one node. " ,                    "The list can't be made empty ");            return;        }          // Copy the data of next node to head        head->data = head->next->data;          // store address of next node        n = head->next;          // Remove the link of next node        head->next = head->next->next;          // free memory        free(n);          return;    }        // When not first node, follow the     // normal deletion process      // Find the previous node    struct Node *prev = head;    while(prev->next != NULL &&           prev->next != n)        prev = prev->next;      // Check if node really exists in     // Linked List    if(prev->next == NULL)    {        printf(        "Given node is not present in Linked List");        return;    }      // Remove node from Linked List    prev->next = prev->next->next;      // Free memory    free(n);      return; }  /* Utility function to insert a    node at the beginning */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;}  /* Utility function to print a    linked list */void printList(struct Node *head){    while(head!=NULL)    {        printf("%d ",head->data);        head=head->next;    }    printf("");}  // Driver codeint main(){    struct Node *head = NULL;      /* Create following linked list       12->15->10->11->5->6->2->3 */    push(&head,3);    push(&head,2);    push(&head,6);    push(&head,5);    push(&head,11);    push(&head,10);    push(&head,15);    push(&head,12);      printf("Given Linked List: ");    printList(head);      /* Let us delete the node with        value 10 */    printf("    Deleting node %d: ",     head->next->next->data);    deleteNode(head,                head->next->next);      printf(    "Modified Linked List: ");    printList(head);      // Let us delete the first node     printf(    "Deleting first node ");    deleteNode(head, head);      printf(    "Modified Linked List: ");    printList(head);      getchar();    return 0;}
Output:
Given Linked List: 12 15 10 11 5 6 2 3

Deleting node 10:
Modified Linked List: 12 15 11 5 6 2 3

Deleting first node
Modified Linked List: 15 11 5 6 2 3
Please refer complete article on Delete a given node in Linked List under given constraints for more details!
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