Thread: I want to delete node

I tried to delete the second node in list

Code:

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

struct Node
{
  int data;
  struct Node *next;
};
  int main()
{
  struct Node* head = NULL;
  struct Node* second = NULL;
  struct Node* third = NULL;

  head  = (struct Node*)malloc(sizeof(struct Node));
  second = (struct Node*)malloc(sizeof(struct Node));
  third  = (struct Node*)malloc(sizeof(struct Node));
 
  head->data = 1;     
  printf(" %d ", head->data);
  head->next = second; 
 
  second->data = 2;     
  printf(" %d ", second->data);
  
  second->next = third;
  
  free(second);
 
  third->data = 3;   
  printf(" %d ", third->data);
  third->next = NULL;

  return 0;
}

1 2 3

free(second);

but It doesn't delete

Oh it deletes it just fine.

Your code is broken because it keeps a second reference to your deleted node (in the form of first->next).

You need to stop hand rolling lists and write some functions like we showed you in other threads.

Code:

int main ( ) {
  struct Node* head = NULL;
  head = insertFront(head,1);
  head = insertFront(head,2);
  head = insertFront(head,3);
  printList(head);
  // search for the node with the value 2 and remove it.
  // repair the list to ensure the node prior to node 2 
  // ends up pointing to the node after 2
  head = deleteNode(head,2);
  printList(head);
}

Deleting a node should only call free()

Why do you want to make a new node, if all you're doing is trying to remove one.

Try something simple first, just remove the first node of the list unconditionally.

Originally Posted by Salem

Deleting a node should only call free()

Why do you want to make a new node, if all you're doing is trying to remove one.

Try something simple first, just remove the first node of the list unconditionally.

I can only remove last node but I want to delete any node

Code:

#include<stdio.h>#include<stdlib.h> 
    
struct node{
  int Number;
  struct node *next;
};
  
struct node* newNode(int number, struct node *next) {
    struct node *new = malloc(sizeof(*new));
           new->Number = number;
           new->next = next;
    return new;
}


  
void show(struct node *head){
     struct node *c;
     c = head;
     while (c!=NULL){
           printf("%d\n",c->Number);
           c = c->next;
           }
   
     }


struct node* deleteNode(int n,  struct node* node)
{
    struct node *first1, *n_th_node, *save;
    int count = 0;
    save = first1 = n_th_node = node;
    while(first1->next)
    {
        first1 = first1->next;
        count++;
        if(count == (n-1))
        break;
    }


    while ( first1->next != NULL )
    {
        first1 = first1->next;
        save = n_th_node;
        n_th_node = n_th_node->next;
    }


    save->next = n_th_node->next;
    free(n_th_node);
    return node;


}


       
int main (void ) {
   struct node *head = NULL;  
    
head = newNode(10, head);
head = newNode(20, head);
head = newNode(30, head);


show(head);
head = deleteNode(2, head);


printf("new list \n");
show(head);
       
    return 0;
}

Your first while loop should be something like

Code:

prev = NULL;
while ( node && count < n ) {
    prev = node;
    node = node->next;
    count++;
}

When the loop exits, you have these conditions to deal with.
1. prev may be NULL
2. node may be NULL
3. count may be == n

Work out what each of those things means for your list.

So what's the purpose of your 2nd while loop.

You only need one while loop, and that one I posted.

At that point, node is pointing to the node you want to delete.
You don't need another loop.

> I tried single while loop in function code doesn't delete specif node.
That's because you didn't read what I wrote.

Originally Posted by myself

When the loop exits, you have these conditions to deal with.
1. prev may be NULL
2. node may be NULL
3. count may be == n

Work out what each of those things means for your list.

Code:

struct node *deleteNode(int n, struct node *head ) {
  struct node *node = head;
  struct node *prev = NULL;
  while ( node && count < n ) {
    prev = node;
    node = node->next;
    count++;
  }

  if ( prev == NULL ) {
    // it's the head node being deleted
    head = node->next;
    free(node);
  } else
  if ( node == NULL ) {
    // ran off the end of the list, nothing to do
  } else {
    prev->next = node->next;
    free(node);
  }
  return head;
}