reverse-LL.c

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

struct node{
    int val;
    struct node *next;
};

void print_list(struct node *head)
{
    printf("H->");

    while(head)
    {
        printf("%d->", head->val);
        head = head->next;
    }

    printf("|||\n\n");
}

void insert_front(struct node **head, int value)
{
    struct node * new_node = NULL;

    new_node = (struct node *)malloc(sizeof(struct node));

    if (new_node == NULL)
    {
        printf("Failed to insert element. Out of memory");
    }

    new_node->val = value;
    new_node->next = *head;

    *head = new_node;
}

void reverse_linked_list(struct node **head) {
  struct node *new_head = NULL; /*head of the reversed list*/
  struct node *tmp = NULL;

  while(*head) {
    tmp = *head; /*tmp points the first node of the current list*/
    *head = (*head)->next;

    /*Insert tmp at the front of the reversed list.*/
    tmp->next = new_head;
    new_head = tmp;
  }

  *head = new_head;
}

void main()
{
    int count = 0, i, val;
    struct node * head = NULL;

    printf("Enter number of elements: ");
    scanf("%d", &count);

    for (i = 0; i < count; i++)
    {
        printf("Enter %dth element: ", i);
        scanf("%d", &val);
        insert_front(&head, val);
    }

    printf("Initial List: ");
    print_list(head);

    reverse_linked_list(&head);

    printf("Reversed List: ");
    print_list(head);
}