postfix using arrays

[robertosp]

HI i am doing a program which takes numbers from a user into postfix, using an array i cannot use the stack library. SO far i have the following i know i need to implement some cases for the +-*/ then popping them out. any help will be appreciated

#include<iostream>;
#include<stdlib.h>;
using namespace std;




class stack
{
    
	int stk[50],top;

	public:
		stack(){
			topstack =-1;
		       }

		void push(int x)
		{
			if (topstack>50)
			{
				cout<<"the stack is full";
				return;
			}
			stk[++topstack]=x;
		         }


		void pop()
		{
		if (top<0)
		{
		cout<<"the stack is empty";
		return;
		}
		


	    }
					
			

		

};



int main () {
	int ch;
	stack st;
	while(1)
	{
		cout <<"\n Press 1 to push \n Press 2 to pop \n  Press 3 to quit ";
		cin >>ch;

		switch(ch)
		{
			case 1: cout<<"Enter Choice:";
			cin>>ch;
					st.push(ch);
			break;
			case 2: st.pop();
			break;
			case 3: exit(0);


		}
		return(0);
	}
}