Ashwani Blog

c code for stack using one queue only

July ,7th ,2022
cstackqueue
write a c code for stack using one queue only

Given one queue data structure. WAP to implement stack using only one queue data structure.

Code

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

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

struct Node *f = NULL;
struct Node *r = NULL;
struct Node *tp = NULL;

void Display(struct Node *ptr)
{
    printf("Elements of this linked list\n");
    while (ptr != NULL)
    {
        printf("Element: %d\n", ptr->data);
        ptr = ptr->next;
    }
}

int isEmpty(struct Node *top)
{
    if (top == NULL)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

int isFull(struct Node *top)
{
    struct Node *p = (struct Node *)malloc(sizeof(struct Node));
    if (p == NULL)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

void enqueue(int val)
{
    struct Node *n = (struct Node *)malloc(sizeof(struct Node));
    if (n == NULL)
    {
        printf("Queue is Full");
    }
    else
    {
        n->data = val;
        n->next = NULL;
        if (f == NULL)
        {
            f = r = n;
        }
        else
        {
            r->next = n;
            r = n;
        }
    }
}

int dequeue()
{
    int val = -1;
    struct Node *ptr = f;
    if (f == NULL)
    {
        printf("Queue is Empty\n");
    }
    else
    {
        f = f->next;
        val = ptr->data;
        free(ptr);
    }
    return val;
}

void push(int val)
{
    if (isFull(tp))
    {
        printf("Stack Overflow! Cannot push %d to the Stack\n", val);
    }
    else
    {
        if (tp == NULL)
        {

            enqueue(val);
            tp = f;
        }
        else
        {
            enqueue(val);
            struct Node *ptr = f;
            while (ptr->next->next != NULL)
            {
                ptr = ptr->next;
            }
            struct Node *n = ptr->next;
            ptr->next = NULL;
            r=ptr;
            n->next = f;
            f = n;
            tp = f;
        }
    }
}

int pop()
{
    int x = dequeue();
    return x;
}

int main()
{
    push(34);
    push(4);
    push(7);
    push(17);
    Display(tp);
    printf("Dequeuing element %d\n", pop());
    printf("Dequeuing element %d\n", pop());
    printf("Dequeuing element %d\n", pop());
    printf("Dequeuing element %d\n", pop());
    return 0;
}