Question

How to reverse linked list below,thank you!

#include <stdlib.h>
#include <stdio.h>
struct list
{
int data;
struct list *next;
};
typedef struct list node;
typedef node *link;
int main()
{
link ptr,head;
int num,i;

head = ( link ) malloc(sizeof(node));
ptr = head;
printf("enter 10 data \n");
for ( i = 0; i <= 9; i++ )
{
scanf("%d",&num);
ptr->data = num;
ptr->next = ( link ) malloc(sizeof(node));
if ( i == 9 )
ptr->next = NULL;
else
ptr = ptr->next;
}
printf("original linked list\n");
ptr = head;
while ( ptr != NULL )
{
printf("data==> %d\n",ptr->data);
ptr = ptr->next;
}
  
system("pause");
return 0;
}

Answer 1

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

struct list
{
int data;
struct list *next;
};

typedef struct list node;
typedef node *link;

list *reverseLinkedList (list *head)
{
   if ( head == NULL)
   {
       return NULL;
   }
   list *temp = head;
   list *curr = head;
   list * pred = NULL;
   while(curr != NULL)
   {
       temp = temp ->next;
       curr->next = pred;
       pred = curr;
       curr = temp;
   }
   head = pred;
   return head;
}
int main()
{
link ptr,head;
int num,i;
head = ( link ) malloc(sizeof(node));
ptr = head;
printf("enter 10 data \n");
for ( i = 0; i <= 9; i++ )
{
scanf("%d",&num);
ptr->data = num;
ptr->next = ( link ) malloc(sizeof(node));
if ( i == 9 )
ptr->next = NULL;
else
ptr = ptr->next;
}
printf("original linked list\n");
ptr = head;
while ( ptr != NULL )
{
printf("data==> %d\n",ptr->data);
ptr = ptr->next;
}
head = reverseLinkedList(head);

printf("reverse linked list\n");
ptr = head;
while ( ptr != NULL )
{
printf("data==> %d\n",ptr->data);
ptr = ptr->next;
}

system("pause");
return 0;
}