stacks.cpp

#include <iostream>
#include <climits>
using namespace std;

class StackUsingArray {
	int *data;
	int nextIndex;
	int capacity;	

	public :

	StackUsingArray() {
		data = new int[10];
		nextIndex = 0;
		capacity = 10;
	}

	// return the number of elements present in my stack
	int size() {
		return nextIndex;
	}

    // check if stack empty or not
	bool isEmpty() {
		if(nextIndex == 0) {
			return true;
		}
		else {
			return false;
		}
    }

	// insert element
	void push(int element) {
		if(nextIndex == capacity) {
            // dynamic stack creation
			int *newData = new int[2 * capacity];
			for(int i = 0; i < capacity; i++) {
				newData[i] = data[i];
			}
			capacity *= 2;
			delete [] data; // deletion of previous dyn allocated memory
			data = newData;
		}
		data[nextIndex] = element;
		nextIndex++;
	}

	// delete element
	int pop() {
		if(isEmpty()) {
			cout << "Stack is empty " << endl;
			return INT_MIN;	
		}
		nextIndex--;
		return data[nextIndex];
	}

	int top() {
		if(isEmpty()) {
			cout << "Stack is empty " << endl;
			return INT_MIN;	
		}
		return data[nextIndex - 1];
	}
};

int main() {
	StackUsingArray s;
	s.push(10);
	s.push(20);
	s.push(30);
	s.push(40);
	s.push(50);

	cout << s.top() << endl;

	cout << s.pop() << endl;
	cout << s.pop() << endl;
	cout << s.pop() << endl;

	cout << s.size() << endl;

	cout << s.isEmpty() << endl;

}