programming-examples/c/Recursion/C Program to Reverse a Stack using Recursion.c

/*
 * C Program to Reverse a Stack using Recursion
 */
#include <stdio.h>
#include <stdlib.h>

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

void generate(struct node **);
void display(struct node *);
void stack_reverse(struct node **, struct node **);
void delete(struct node **);

int main()
{
    struct node *head = NULL;
    generate(&head);
    printf("\nThe sequence of contents in stack\n");
    display(head);
    printf("\nInversing the contents of the stack\n");
    if (head != NULL)
        {
            stack_reverse(&head, &(head->next));
        }
    printf("\nThe contents in stack after reversal\n");
    display(head);
    delete(&head);
    return 0;
}

void stack_reverse(struct node **head, struct node **head_next)
{
    struct node *temp;
    if (*head_next != NULL)
        {
            temp = (*head_next)->next;
            (*head_next)->next = (*head);
            *head = *head_next;
            *head_next = temp;
            stack_reverse(head, head_next);
        }
}

void display(struct node *head)
{
    if (head != NULL)
        {
            printf("%d  ", head->a);
            display(head->next);
        }
}

void generate(struct node **head)
{
    int num, i;
    struct node *temp;
    printf("Enter length of list: ");
    scanf("%d", &num);
    for (i = num; i > 0; i--)
        {
            temp = (struct node *)malloc(sizeof(struct node));
            temp->a = i;
            if (*head == NULL)
                {
                    *head = temp;
                    (*head)->next = NULL;
                }
            else
                {
                    temp->next = *head;
                    *head = temp;
                }
        }
}

void delete(struct node **head)
{
    struct node *temp;
    while (*head != NULL)
        {
            temp = *head;
            *head = (*head)->next;
            free(temp);
        }
}