weird number appears on output-C - c

Question

I have made a simple list like this:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <conio.h>
struct node{
int am;
struct node *next;
};
typedef struct node node;
int main(){
int n;
node *head=(node *)malloc(sizeof(node));
node *cur=head;
printf("Give me a number:\n");
scanf(" %d",head->am);
cur=head;
while(1){
printf("Give me a number\n");
scanf(" %d",&n);
if(n==0)
break;
cur->am=n;
cur->next=(node *)malloc(sizeof(node));
cur=cur->next;
cur->next=null;
}
travel(head);
printf("Total nodes available :%d\n",count(head));
system("pause");
return 0;
}
Now travel is supposed to go through each node in the list and display the integer saved in each node.
void travel(node *h){
if(h==NULL)
return;
printf("Received data from node: \t %d\n",h->am);
travel(h->next);
}
Now the problem is that when travel is called it wont print the integer from the first node.It will also print another "Received data from node:" followed by a strange number.
For example
If i give 1,2,3,4 as inputs these are the results
Received data from node: 2
Received data from node: 3
Received data from node: 4
Received data from node: 4026432
Any ideas?

Answer 1

Now the problem is that when travel is called it wont print the
integer from the first node
This can be precisely known from this part of the main() function
printf("Give me a number:\n");
scanf(" %d",head->am); //this is wrong use of scanf("%d",&head->am);
cur=head;
while(1){
printf("Give me a number\n");
scanf(" %d",&n);
if(n==0)
break;
cur->am=n;
as I've mentioned you're scanning wrongly but that doesn't matter because later in the code in while loop you replace it this way...
you scan number and store it at head->am
then you assign head to cur so head->am and cur->am are both the same now... so in while loop when you first assign n to cur->am, it gets assigned to head->am. so this explains why you never get to print first node.
Solution:
to overcome it ... in while loop, before assigning cur->am=n try doing:
cur->next=(node *)malloc(sizeof(node));
cur=cur->next;
//then... assign
curr->am=n;
this way you'll not lose first node.
suggestion:
As someone has already said it's much easier to traverse/ travel the list using loops (never mind... if you want to do it recursively)
here's how you do it with the loops:
void travel(node *h)
{
if(h==NULL)
return; //list is empty,consider printing "list empty" :)
while(h!=NULL)
{
printf("Received data from node: \t %d\n",h->am);
h=h->next;
}
}
To put all together your code without changing the travel() function as suggested would be:
#include <stdio.h>
#include <stdlib.h>
struct node
{
int am;
struct node *next;
};
typedef struct node node;
void travel(node *h);
int main() //I have a habit of returning values from main() :)
{
int n;
node *head=(node *)malloc(sizeof(node));
node *cur=head;
printf("Give me a number:\n");
scanf(" %d",&head->am);
cur=head;
while(1)
{
printf("Give me a number\n");
scanf(" %d",&n);
if(n==0)
break;
cur->next=(node *)malloc(sizeof(node));
cur=cur->next;
cur->am=n; //NOTE:here's the change!
cur->next=NULL;
}
travel(head);
return 0; //just to signify successful compilation
}
void travel(node *h)
{
if(h==NULL)
return;
printf("Received data from node: \t %d\n",h->am);
travel(h->next);
}
Sample Input : 5 6 3 1 0
Sample Output :
Give me a number:
5
Give me a number
6
Give me a number
3
Give me a number
1
Give me a number
0
Received data from node: 5
Received data from node: 6
Received data from node: 3
Received data from node: 1

Answer 2

There are (at least) those issues:
The line scanf(" %d",head->am) is wrong since scanf() expects an address of the memory location of the expected value meaning &head->am.
Your loop scans a number and puts it in the current node and only after it creates a new node. Therefore, the first number you enter will be overridden (after fixing the first issue) and the last node created will contain random data because the loop will terminate after entering 0 but before putting anything in the last node.

Answer 3

I propose like this:
int main(void){
int n;
node anchor = {0, NULL};//dummy head
node *head, *cur = &anchor;
while(1){
printf("Give me a number\n");
scanf("%d", &n);
if(n==0)
break;
cur->next = malloc(sizeof(node));
cur = cur->next;
cur->am = n;
cur->next = NULL;
}
head = anchor.next;
travel(head);
printf("Total nodes available :%d\n", count(head));
return 0;
}

Answer 4

You are missing & at the first scanf:
scanf(" %d", &head->am);
But it could be made to do all the scanf inside the while:
int main(){
node *head=0;
node *cur=0;
node *prev=0;
while(1){
prev = cur;
cur=(node *)malloc(sizeof(node));
cur->next=NULL;
printf("Give me a number\n");
scanf("%d",&cur->am);
if(cur->am==0)
break;
if(head == NULL) head = cur;
if(prev != NULL) prev->next = cur;
}
travel(head);
printf("Total nodes available :%d\n",count(head));
return 0;
}
I hope I didnt make any mistake as I wrote it in this SO editor..
and as someone said, you should free the linked list .. but thats out of scope here..
HTH