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

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

struct Node* top = NULL;

void push() {
    int value;
    printf("Enter value to push: ");
    scanf("%d", &value);

    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    if (newNode == NULL) {
        printf("Stack Overflow (Memory allocation failed)\n");
        return;
    }
    newNode->data = value;
    newNode->next = top;
    top = newNode;
    printf("%d pushed to stack\n", value);
}

void pop() {
    if (top == NULL) {
        printf("Stack Underflow! Cannot pop from empty stack.\n");
        return;
    }
    struct Node* temp = top;
    int poppedValue = temp->data;
    top = top->next;
    free(temp);
    printf("Popped value: %d\n", poppedValue);
}

void peek() {
    if (top == NULL) {
        printf("Stack is empty, nothing to peek.\n");
        return;
    }
    printf("Top element is: %d\n", top->data);
}

void display() {
    if (top == NULL) {
        printf("Stack is empty.\n");
        return;
    }
    struct Node* temp = top;
    printf("Stack elements (top to bottom): ");
    while (temp != NULL) {
        printf("%d ", temp->data);
        temp = temp->next;
    }
    printf("\n");
}

int main() {
    int choice;

    while (1) {
        printf("\nStack Operations Menu:\n");
        printf("1. Push\n");
        printf("2. Pop\n");
        printf("3. Peek\n");
        printf("4. Display\n");
        printf("5. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                push();
                break;

            case 2:
                pop();
                break;

            case 3:
                peek();
                break;

            case 4:
                display();
                break;

            case 5:
                printf("Exiting program.\n");
                return 0;

            default:
                printf("Invalid choice! Please try again.\n");
                break;
        }
    }

    return 0;
}