No program output in C [closed] - c

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Closed 10 years ago.
#include<stdio.h>
#include<malloc.h>
typedef struct node_t {
int i;
struct node_t* link;
} node;
node* head = NULL;
int main() {
int i = 10;
node* temp = NULL;
head = (node *)malloc(sizeof(node));
temp = (node *)malloc(sizeof(node));
if(temp == NULL) {
printf("\n malloc for temp node failed! \n");
}
else {
/* linked list logic to add the elements in the beginning */
while(i<=10) {
temp->i = i;
temp->link = NULL;
if(head == NULL) {
head = temp;
}
else {
temp->link = head;
head = temp;
}
i++;
}
}
for(temp = head; temp->link != NULL; temp = temp->link) {
printf("\n The data is:%d \n",temp->i);
}
free(temp);
free(head);
return 0;
}
I'm trying a simple linked list program. I'm not getting the output.

Answer 1

1) You have to allocate node (tmp) each time you are assigning value to tmp. and not allocate only one time the tmp. See the following fixed code to see how to do it
2) the following for loop is wrong:
for(temp = head; temp->link != NULL; temp = temp->link) {
This for loop is fixed in the following code
3) for the free you have to browse the whole linked list and then free each node. see the following fixed code.
#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
typedef struct node_t{
int i;
struct node_t* link;
}node;
node* head = NULL;
int main(){
int i = 1;
node* temp = NULL;
/* linked list logic to add the elements in the beginning */
while(i<=10){
temp = (node *)malloc(sizeof(node));
if(temp == NULL){
printf("\n malloc for temp node failed! \n");
exit(1);
}
temp->i = i;
temp->link = NULL;
if(head == NULL){
head = temp;
}
else{
temp->link = head;
head = temp;
}
i++;
}
for(temp = head; temp != NULL; temp = temp->link){
printf("\n The data is:%d \n",temp->i);
}
while (head!=NULL)
{
temp = head->link;
free(head);
head = temp;
}
}

Answer 2

You seem to have an infinite loop! (the value of i is not changed)

Answer 3

You are not changing the value of variable i in the while loop as a result you never come out of the while loop.
You need something like:
int i=1;
while(i<=10){
// insert i in loop
i++;
}

Answer 4

You are not changing the value of loop variable i.e. i.
Also you need to do malloc inside while loop to create separate nodes. Right now, your code is modifying the same node again and again.

Answer 5

In addition to the node about the infinite loop, since you never modify the value of i there's something else that's wrong.
22 /* linked list logic to add the elements in the beginning */
23 while(i<=10){
24 temp->i = i;
25 temp->link = NULL;
26 if(head == NULL){
27 head = temp;
28 }
29 else{
30 temp->link = head;
31 head = temp;
Look at what you are doing in this loop. If head is NULL (it's very unlikely to be, since you allocated it back in line 15, although it's possible that the allocation could fail) you set 'head' to temp.
If head is not NULL, you set temp's 'link' to head. Then you set head to temp. Then you loop and do it all over again.
So you end up with head pointing to temp, and temp->link pointing to temp... a circular list of exactly one node.
Try this instead:
int main()
{
int i = 0;
node *temp;
/* linked list logic to add the elements in the beginning */
while(i != 10)
{
/* First, allocate a new node */
temp = (node *)malloc(sizeof(node));
if(temp == NULL)
return -1; /* yikes */
/* now set its value */
temp->i = i++;
/* and link it into the list, at the beginning */
temp->link = head;
head = temp;
}
/* Now traverse the list, starting from 'head' */
temp = head;
while(temp != NULL)
{
/* save the current node in a temporary variable */
node *temp2 = temp;
/* and move 'temp' to point to the next node in the list */
temp = temp->link;
/* print the current node */
printf("\n The data is: %d\n", temp2->i);
/* and free the memory */
free(temp2);
}
return 0;
}