#ifndef STACK_H #define STACK_H

#include

// Node structure for stack struct StackNode { int data; StackNode* next;

StackNode(int val) { data = val; next = NULL; // changed from nullptr to NULL } };

// Stack class using linked list class Stack { private: StackNode* top;

public: // Constructor Stack() { top = NULL; // changed from nullptr to NULL }

// Push an element onto the stack void push(int val) { StackNode* newNode = new StackNode(val); newNode->next = top; top = newNode; }

// Pop an element from the stack int pop() { if (isEmpty()) { std::cout << "Stack Underflow!" << std::endl; return -1; } StackNode* temp = top; int popped = temp->data; top = top->next; delete temp; return popped; }

// Peek at the top element int peek() const { if (isEmpty()) { std::cout << "Stack is empty!" << std::endl; return -1; } return top->data; }

// Check if the stack is empty bool isEmpty() const { return top == NULL; // changed from nullptr to NULL }

// Display the stack elements void display() const { StackNode* current = top; std::cout << "Stack (top to bottom): "; while (current != NULL) { std::cout << current->data << " "; current = current->next; } std::cout << std::endl; }

// Destructor to clean up memory ~Stack() { while (!isEmpty()) { pop(); } } };

#endif // STACK_H