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C program to delete node from single linked list when just address of the previous node to be deleted is given

shiv@ubuntu:~/ds/list$ cat deln.c
/*
 * C Program to delete node in the single linked list, when address of the
 *previous  node to be deleted is given
 */

#include <stdio.h>
#include <stdlib.h>

struct list {
    int d;
    struct list *next;
};

/*
 * function to delete node when just address of the node to be
 * deleted is given in the single linked list
 */
void deletenode(void **ptr)
{
  struct list **temp, *del;

  if(*ptr == NULL) {
     printf("Invalid pointer\n");
     return;
  }
  temp= (struct list **)ptr;
  printf("The address of previous node of the node to be deleted is %p data %d\n", *temp, (*temp)->d);

  if((*temp)->next && (*temp)->next->next){
     /* any node apart from node before last or last node in the list */
     (*temp)->d = (*temp)->next->d;
     del = (*temp)->next;
     (*temp)->next = (*temp)->next->next;
     free(del);
  } else if((*temp)->next) {
           /* This is  node before last node */
            (*temp)->d = (*temp)->next->d;
            free((*temp)->next);
            (*temp)->next = NULL;
  } else {
       /* this is last node we can't delete from it's previous node next pointer
        * but we can free it and make it NULL, really we can't delete last node
        * it is not possible to remove
        */
       free(*temp);
       (*temp)=NULL;
  }
   
}

void display(struct list *temp)
{
 printf("Elements in list are\n");
 while(temp != NULL){
        printf("ADDR %p data %d next %p\n", temp, temp->d, temp->next);
        temp=temp->next;
 }

}
int main()
{
  struct list *head=NULL, *temp;
  void *ptr;

  /* testing program by creating list from below array */
  int a[]={1 ,3 ,4,5,6,7,8,9};
  int i;

  for(i=0;i<8; i++)
  {
     temp=malloc(sizeof(struct list));
     if(!temp){
    return;
     }
     temp->d = a[i];
     temp->next = NULL;
     if(head == NULL){
    head = temp;
     } else {
        temp->next = head;
    head = temp;
    }
 }

 display(head); /* display list before deleting */
 printf("Enter address of previous node to be deleted\n");
 scanf("%p", &ptr);
 deletenode(&ptr);
 display(head);  /* display list after delete */
}
/* end of the program */



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