stack.cpp

#include <iostream>
using namespace std;

//------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
/*
STACK

--> OPERATIONS
1) push() -
	Place an item onto the stack. If there is no place for new item, stack is in overflow state.

2) pop() -
	Return the item at the top of the stack and then remove it. If pop is called when stack is empty, it is in an underflow state.

3) isEmpty() -
	Tells if the stack is empty or not

4) isfull() -
	Tells if the stack is full or not.

5) peek() -
	Access the item at the i position

6) count() -
	Get the number of items in the stack.

7) change() -
	Change the item at the i position

8) display() -
	Display all items in the stack

*/
//------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

class stack
{
private:
	int top = -1;
	int size = (int)1e5;
	int arr[(int)1e5];

public:
	stack()
	{
		for (int i = 0; i < size; ++i)
		{
			arr[i] = 0;
		}
	}
	// stack() {
	// 	cout << "Enter size of stack :  ";
	// 	cin >> size;
	// 	int arr[size] ;
	// 	for (int i = 0; i < size; ++i)
	// 	{
	// 		arr[i] = 0 ;
	// 	}
	// }

	void push(int num)
	{
		top++;
		if (top < size)
		{
			arr[top] = num;
		}
		else
		{
			top--;
			cout << "stack is full" << endl;
		}
	}

	void pop()
	{
		if (top != -1)
		{
			arr[top] = 0;
			top--;
		}
		else
		{
			cout << "stack is empty" << endl;
		}
	}

	bool isEmpty()
	{
		if (top == -1)
			return true;
		else
			return false;
	}

	bool isFull()
	{
		if (top == (size - 1))
			return true;
		return false;
	}

	int peek()
	{
		if (isEmpty()) {
			cout<<"Stack is Empty"<<endl;
			return INT_MIN;
		}
		return arr[top];
	}

	int count()
	{
		return top + 1;
	}

	void change(int i, int newVel)
	{
		arr[i] = newVel;
	}

	void display()
	{
		for (int i = 0; i < top + 1; ++i)
		{
			cout << arr[i] << " ";
		}
		cout << endl;
	}
};

int main()
{

	stack s;

	int ans,val,index;
	do
	{
		cout<<"\n1. push()\n2.pop()\n3. isEmpty()\n4. isFull\n5. peek() \n6.count() \n7.change() \n8. display()\n0. Exit \n\nEnter your ans :   ";
	cin>>ans;
		switch (ans)
		{
		case 1:
			cout<<"Enter value :   ";
			cin>>val;
			s.push(val);
			break;
		
		case 2:
			s.pop();
			break;

		case 3:
			cout<<((s.isEmpty())?"YES":"NO")<<endl;
			break;

		case 4:
			cout<<((s.isFull())?"YES":"NO")<<endl;
			break;
		
		case 5:
		 	cout<<s.peek()<<endl;
			break;
		
		case 6:
			cout<<s.count()<<endl;
			break;

		case 7:
			cout<<"Enter index :   ";
			cin>>index;
			cout<<"Enter val :   ";
			cin>>val;
			s.change(index ,val);
			break;

		case 8:
			s.display();
			break;

		default:
			break;
		}

	} while (ans);

	return 0;
}