not woking c program for SLL

Question

Q please help me this program is not working properly. not displaying the value.this program is an example of singly linked list which I am trying to run on c. `

#include<stdio.h>
 #include<stdlib.h>        //malloc defined
struct node       
{
       int data;
       struct node *next;      
       };
 add()      //add function
  {
      int value;
       struct node *n;
       n=(struct node*)malloc(sizeof(struct node));  //mem allocation
       printf("enter the value to add\n");
       scanf("%d",&value);
       n->data=value;
       n->next=NULL;
      // n=n->next;
      // n->next=NULL;
       }  
  delete()     //delete function
  {
       //   n=n->next;
          struct node *n;    //declaration
          printf("the node deleted is %d",n->data);
          free(n);
          }

  display()          //display function
  {
           struct node *n;
           while(n!=NULL)
             {
             printf("%d",n->data);
             n=n->next;

             }
           }             
int main()
{
     int ch;
     while(1)
     {
             printf("do you want to add node press 1\n");

             printf("do you want to delete node press 2\n");

             printf("do you want to display node press 3\n");

             printf("do you want to exit press 4\n");
             scanf("%d",&ch);
     switch(ch)
     {
        case 1:add();
               break;

        case 2:delete();
               break;

        case 3:display();
               break;

        case 4:exit(0);


        default: printf("wrong choice!!!\n");                                      

     }
     }
     return 0;
     getch();
     }
 please help me this program is not working properly.

not displaying the value.this program is an example of singly linked list which I am trying to run on c.

Local variables defined inside function are, well, *local*, and exist only inside the functions they are declared in. A variable named `n` inside the function `add` is different from a variable with the same name in another function. — Some programmer dude, Feb 25 '16 at 06:59
It also looks to me like you need to find a good beginners book, so I suggest you check out [The Definitive C Book Guide and List](http://stackoverflow.com/questions/562303/the-definitive-c-book-guide-and-list). — Some programmer dude, Feb 25 '16 at 07:00
Yes sir I need to work more on my C skills thanks for your recommendation about the book — prajyot, Feb 26 '16 at 08:00

Andreas DM · Answer 1 · 2016-02-25T07:11:51.587

0

printf("%d",n->data); is not printed because:

struct node *n;  // n is not determined.
while(n != NULL) // undefined behaviour

n is different from the other n that is in the add() function. You never passed the struct to the other functions so it will not do what you wanted it to do.

edited Feb 25 '16 at 07:11

answered Feb 25 '16 at 07:02

Andreas DM

10,685
6
35
62

One small problem: Local variables are not initialized, so saying that `n` is `NULL` is wrong. The value of `n` is *indeterminate* (and will in reality seem random). Using such variables except to initialize them leads to *undefined behavior*. – Some programmer dude Feb 25 '16 at 07:06
@JoachimPileborg Thanks :) – Andreas DM Feb 25 '16 at 07:06

score 0 · Answer 2 · answered Feb 25 '16 at 07:13

0

in the function display(), the local variable 'n' is only declared but not defined, so here 'n' is only a wild pointer. It's happened in the function delete() as well.
it's not a correct way to implement the single linked list. In the function add() what you wrote is only create a node, but not add a node to linked list.

answered Feb 25 '16 at 07:13

zhaolin chi

1
1

yes I agree zhaolin chi – prajyot Feb 26 '16 at 07:47

score 0 · Accepted Answer · answered Feb 26 '16 at 12:56

 #include<stdio.h>
 #include<stdlib.h>        //malloc defined
struct node       
    {
       int data;
       struct node *next;      
       }*n,*p;

 create()      //add function
  {
      int value;

       n=(struct node*)malloc(sizeof(struct node));  //mem allocation
       printf("enter the value to add\n");
       scanf("%d",&value);
       n->data=value;
       n->next=NULL;

        }  
   add()
   {    
   int value;
//    struct node *p;
     p=(struct node*)malloc(sizeof(struct node));
    printf("enter the value to add next\n");
    scanf("%d",&value);
   n->next=p;
   p->data=value;
   p->next=NULL;

    }    
  delete()     //delete function
  {

          printf("the node deleted is %d",p->data);
           n->next=NULL;
          free(p);   

            }

      display()          //display function
      {

               while(n!=NULL)
                 {
                 printf("%d\n",n->data);
                 n=n->next;

             }
           }             
int main()
{
     int ch;
     while(1)
     {
         printf("do you want to create node press 1\n");
         printf("do you want to add node press 2\n");
         printf("do you want to delete node press 3\n");
         printf("do you want to display node press 4\n");
         printf("do you want to exit press 5\n");
         scanf("%d",&ch);
 switch(ch)
 {
    case 1:create();
           break;

    case 2:add();
           break;

    case 3:delete();
           break;

    case 4:display();
           break;

    case 5:exit(0);


    default: printf("wrong choice!!!\n");                                      

 }
 }
 return 0;
 getch();
 }

not woking c program for SLL

3 Answers3