Solution.c

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

#define MAX 100

typedef struct Stack {
    int arr[MAX];
    int top;
} Stack;

void initStack(Stack* s) {
    s->top = -1;
}

int isEmpty(Stack* s) {
    return s->top == -1;
}

int isFull(Stack* s) {
    return s->top == MAX - 1;
}

void push(Stack* s, int value) {
    if (isFull(s)) {
        printf("Stack Overflow\n");
        return;
    }
    s->arr[++s->top] = value;
}

int pop(Stack* s) {
    if (isEmpty(s)) {
        printf("Stack Underflow\n");
        return -1;
    }
    return s->arr[s->top--];
}

typedef struct Queue {
    Stack s1, s2;
} Queue;

void initQueue(Queue* q) {
    initStack(&q->s1);
    initStack(&q->s2);
}

void enqueue(Queue* q, int value) {
    push(&q->s1, value);
}

int dequeue(Queue* q) {
    if (isEmpty(&q->s2)) {
        while (!isEmpty(&q->s1)) {
            push(&q->s2, pop(&q->s1));
        }
    }
    return pop(&q->s2);
}

int main() {
    Queue q;
    initQueue(&q);
    int choice, value;

    do {
        printf("\n1. Enqueue\n2. Dequeue\n3. Exit\nEnter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
        case 1:
            printf("Enter value to enqueue: ");
            scanf("%d", &value);
            enqueue(&q, value);
            break;
        case 2:
            value = dequeue(&q);
            if (value != -1)
                printf("Dequeued value: %d\n", value);
            break;
        case 3:
            printf("Exiting...\n");
            break;
        default:
            printf("Invalid choice\n");
        }
    } while (choice != 3);

    return 0;
}