#include <stdio.h>
#include <stdlib.h>
 
// Structure for Stack
struct Stack {
    int *arr;
    int top;
    int capacity;
};
 
// Function prototypes
void initialize(struct Stack *stack, int capacity);
int isFull(struct Stack *stack);
int isEmpty(struct Stack *stack);
void push(struct Stack *stack, int value);
int pop(struct Stack *stack);
int peek(struct Stack *stack);
void display(struct Stack *stack);
 
int main() {
    struct Stack stack;
    int capacity, choice, value;
 
    printf("Enter the maximum size of stack: ");
    scanf("%d", &capacity);
 
    initialize(&stack, capacity);
 
    do {
        printf("\n--- Stack Operations Menu ---\n");
        printf("1. Push\n");
        printf("2. Pop\n");
        printf("3. Peek (Top Element)\n");
        printf("4. Display Stack\n");
        printf("0. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);
 
        switch (choice) {
            case 1:
                printf("Enter value to push: ");
                scanf("%d", &value);
                push(&stack, value);
                break;
            case 2:
                value = pop(&stack);
                if (value != -1)
                    printf("Popped value: %d\n", value);
                break;
            case 3:
                value = peek(&stack);
                if (value != -1)
                    printf("Top element: %d\n", value);
                break;
            case 4:
                display(&stack);
                break;
            case 0:
                printf("Exiting program.\n");
                break;
            default:
                printf("Invalid choice!\n");
        }
    } while (choice != 0);
 
    // Free dynamically allocated memory
    free(stack.arr);
 
    return 0;
}
 
// Function to initialize stack
void initialize(struct Stack *stack, int capacity) {
    stack->capacity = capacity;
    stack->top = -1;
    stack->arr = (int *) malloc(stack->capacity * sizeof(int));
 
    if (stack->arr == NULL) {
        printf("Memory allocation failed!\n");
        exit(1);
    }
}
 
// Check if stack is full
int isFull(struct Stack *stack) {
    return stack->top == stack->capacity - 1;
}
 
// Check if stack is empty
int isEmpty(struct Stack *stack) {
    return stack->top == -1;
}
 
// Push operation
void push(struct Stack *stack, int value) {
    if (isFull(stack)) {
        printf("Stack Overflow! Cannot push %d\n", value);
        return;
    }
    stack->arr[++stack->top] = value;
    printf("%d pushed to stack.\n", value);
}
 
// Pop operation
int pop(struct Stack *stack) {
    if (isEmpty(stack)) {
        printf("Stack Underflow! No elements to pop.\n");
        return -1;
    }
    return stack->arr[stack->top--];
}
 
// Peek operation
int peek(struct Stack *stack) {
    if (isEmpty(stack)) {
        printf("Stack is empty!\n");
        return -1;
    }
    return stack->arr[stack->top];
}
 
// Display stack elements
void display(struct Stack *stack) {
    if (isEmpty(stack)) {
        printf("Stack is empty!\n");
        return;
    }
 
    printf("\nStack elements (Top to Bottom):\n");
    for (int i = stack->top; i >= 0; i--) {
        printf("%d\n", stack->arr[i]);
    }
}