My code is not working why ?

My code is not working as it supposed to do. code compile with no errors but it doesn't give the output as expected

What's wrong with the code

Code:

---

#include<stdio.h>

#include<stdlib.h>


struct node   
{
  int x;
  struct node *next; 
};


int main () 
{
  struct node *current = NULL;
  struct node *last = NULL;
  struct node *head = NULL;
       
  current = malloc(sizeof(*current));
  last = malloc(sizeof(*last));
 
 
  while ( current!= NULL)
  {
          current->x = 10;
          current->next = last;
         
          current->x = 30;
          current->next = NULL;
  }
 
  head = current;
 
  while (head != NULL)
  {
          printf("%d\n", head->x);
      head = head-> next;
  }
  return 0;
}

---

You haven't said what you expect the code to do, but assuming that you want to insert a few nodes into a linked list and then print them out, how about:

Code:

---

#include <stdio.h>
#include <stdlib.h>
 
typedef struct Node Node;
 
struct Node {
    int  data;
    Node *next;
};
 
int main() {
    Node *head = NULL;
 
    for (int i = 0; i < 5; ++i) {
        Node *nd = malloc(sizeof *nd);
        nd->data = i * 10;
        nd->next = head;
        head = nd;
    }
 
    for (const Node *nd = head; nd; nd = nd->next)
        printf("%d ", nd->data);
    putchar('\n');
 
    return 0;
}

---

It's a good idea to write a function to create the nodes:

Code:

---

#include <stdio.h>
#include <stdlib.h>
 
typedef struct Node Node;
 
struct Node {
    int  data;
    Node *next;
};
 
Node *new_node(int data, Node *next) {
    Node *nd = malloc(sizeof *nd);
    if (!nd) {
        perror("new_node");
        exit(EXIT_FAILURE);
    }
    nd->data = data;
    nd->next = next;
    return nd;
}
 
int main() {
    Node *head = NULL;
 
    for (int i = 0; i < 5; ++i)
        head = new_node(i * 10, head);
 
    for (const Node *nd = head; nd; nd = nd->next)
        printf("%d ", nd->data);
    putchar('\n');
 
    return 0;
}

---

Quote:

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Originally Posted by john.c

You haven't said what you expect the code to do, but assuming that you want to insert a few nodes into a linked list and then print them out, how about:

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I want to add two nodes into linked list and then print out them

I wanted to know whats wrong with my code Why it's not printing two nodes. Whats wrong with code ?

Quote:

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Originally Posted by gajya

I want to add two nodes into linked list and then print out them

I wanted to know whats wrong with my code Why it's not printing two nodes. Whats wrong with code ?

---

Code:

---

  while ( current!= NULL)
  {
      current->x = 10;
      current->next = last;
       
      current->x = 30;        /* You're immediately writing over the same node */

      current->next = NULL;    /* with different values */

---

perhaps you meant

Code:

---


      current->x = 10;
      current->next = last;
       
      last->x = 30;
      last->next = NULL;

---

I have no idea what you're trying to do with the while loop... current is never going to become NULL so it's an infinite loop. Get rid of it

But if you know you only ever want 2 nodes you'd use an array. Otherwise you'd write something along the lines of what john.c wrote

Quote:

---

Originally Posted by Hodor

I have no idea what you're trying to do with the while loop... current is never going to become NULL so it's an infinite loop. Get rid of it

But if you know you only ever want 2 nodes you'd use an array. Otherwise you'd write something along the lines of what john.c wrote

---

following code works for me

Code:

---

#include<stdio.h>#include<stdlib.h>
 
struct node   
{
  int x;
  struct node *next; 
};
 
int main () 
{
  struct node *current = NULL;
  struct node *last = NULL;
  struct node *head;
   
  current = malloc(sizeof(*current));
  last = malloc(sizeof(*last));
 
  current->x = 10;
  current->next = last;
       
  last->x = 30;
  last->next = NULL;
 
  head = current;
 
  while (head != NULL)
  {
      printf("%d\n", head->x);
      head = head-> next;
  }
  free(current);
  free(last);
  free(head);
  return 0;
}

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I think there is one problem in the code I never check weather memory is allocated or not allocated that should I check before