Evaluation of a Postfix Expression.

#define MAX 10
#include "iostream"
#include "cmath"

using namespace std;

class myStack {
    int top;
    int store[MAX];
public:
    void stack_initialize();
    void push(int);
    void pop();
    int get_top();
    void show();
};

void myStack::stack_initialize() {
    top = -1;
}
void myStack::push(int X) {
    if (top >= MAX - 1) {
        cout << "\nOverFlow Error : Your stack is full.\n";
    } else {
        top++;
        store[top] = X;
        cout << "\nPush done..!" << endl;
    }
}
void myStack::pop() {
    if (top < 0) {
        cout << "\nUnderFlow Error : Your stack is empty.\n";
    } else {
        top--;
        cout << "\nPop done..!" << endl;
    }
}
int myStack::get_top() {
    return store[top];
}
void myStack::show() {
    for (int i = top; i >= 0; i--) {
        cout << "|" << store[i] << "|" << endl;
    }
}

int main() {
    string postfix; myStack ss;
    cout << "Give your Arithmetic Expression in Postfix notation (Put space between different operands and operators)." << endl;
    cout << "\nLike : 2 3 * -21 - 3 / 5 33 * +   , which evaluates 174." << endl;
    cout << "\nPostfix Expression : "; getline(cin, postfix); ss.stack_initialize();
    for (int i = 0; postfix[i] != '\0'; i++) {
        if (int(postfix[i]) >= 48 && int(postfix[i]) <= 57) {
            int num = int(postfix[i]) - 48;
            if (postfix[i + 1] == ' ') {
                ss.push(num);
            } else {
                i++;
                while (int(postfix[i]) >= 48 && int(postfix[i]) <= 57) {
                    num *= 10;
                    num += (int(postfix[i]) - 48);
                    i++;
                }
                i--;
                ss.push(num);
            }
        }
        else if (postfix[i] == ' ') continue;
        else if (postfix[i] == '-') {
            if (postfix[i + 1] == ' ' || postfix[i + 1] == '\0') {
                int y = ss.get_top(); ss.pop();
                int x = ss.get_top(); ss.pop();
                ss.push(x - y);
            } else {
                i++;
                int num = int(postfix[i++]) - 48;
                while (int(postfix[i]) >= 48 && int(postfix[i]) <= 57) {
                    num *= 10;
                    num += (int(postfix[i]) - 48);
                    i++;
                }
                i--;
                ss.push( -1 * num);
            }
        }
        else {
            int y = ss.get_top(); ss.pop();
            int x = ss.get_top(); ss.pop();
            if (postfix[i] == '+' ) {
                ss.push(x + y);
            }
            else if (postfix[i] == '*') {
                ss.push(x * y);
            }
            else if (postfix[i] == '/') {
                ss.push(x / y);
            }
            else if (postfix[i] == '^') {
                ss.push(pow(x, y));
            }
            else if (postfix[i] == '%') {
                ss.push(x % y);
            }
        }
    }
    cout << "\n\nEvaluation done, Ans: " << ss.get_top() << "." << endl;
    return 0;
}