Thread: Simple linked list example error.

Hello again.

I was studying Linked list, I'm beginner. Where is my mistake ? Please help me.

Code:

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


struct listnode{
    int num;
    struct listnode *nextPtr;
};
typedef struct listnode ListNode;
ListNode *head, *p;


int main(){


    int choice = 1;


    p = (ListNode*)malloc(sizeof(ListNode));


    head = p;
    while(choice){
    printf("Enter number: ");
    scanf("%d",&p->num);


    p = p->nextPtr;
    p = (ListNode*)malloc(sizeof(ListNode));


    printf("Continue or break(1-0)");
    scanf("%d",&choice);


    }
    p->nextPtr = NULL;
    traverseTheList();
return 0;
}


void traverseTheList(){
    p = head;
    printf("\n");
    printf("\n");
    while( p!=NULL ){
        printf("%d",p->num);
        p = p->nextPtr;
        printf("\n");


    }
}

Code:

p = p->nextPtr;
p = (ListNode*)malloc(sizeof(ListNode));

This is not how you would append a node. Instead, try allocating memory to another variable, assign that value to "p->nextPtr", then advance "p".

Not the most pretty way to go about it, but this should get you rolling. There are other issues, but you can start with that.

Some general comments:

• You should check that "malloc()" succeeds before trying to use the memory
• You should be freeing any of the memory you allocate
• You should not cast the return value of "malloc()": FAQ > Casting malloc - Cprogramming.com
• If you define the function "traverseTheList()" after "main()", you should declare it before
• You should not use global variables, but instead declare them where used and pass them to functions as needed

thank you so much. that's fixed