Hw2-Expression

#include <iostream>
#include <cmath>
#include <vector>

using namespace std;


bool isOperation(char sym)
{
    return sym == '+' || sym == '-' || sym == '*' || sym == '/' || sym == '%';
}

int main()
{
    int result, cntDigit = 0, num = 0;
    vector<int> numbers;
    vector<char> operations;
    string expr;

    cout << "Enter expression: ";
    getline(cin, expr);

    for (int i = expr.length() - 1; i >= 0; i--)
    {

        if (isdigit(expr[i]))
        {
            num += (int)(expr[i] - '0') * pow(10, cntDigit);
            cntDigit++;
        }
        else if (isOperation(expr[i]))
        {
            operations.insert(operations.begin(), expr[i]);
            numbers.insert(numbers.begin(), num);
            cntDigit = 0;
            num = 0;
        }
    }
    numbers.insert(numbers.begin(), num);

    result = numbers.at(0);
    for (int i = 0; i < operations.size(); i++)
    {
        switch (operations.at(i))
        {
            case '+': result += numbers.at(i+1); break;
            case '-': result -= numbers.at(i+1); break;
            case '*': result *= numbers.at(i+1); break;
            case '/': result /= numbers.at(i+1); break;
            case '%': result %= numbers.at(i+1); break;
        }
    }

    cout << expr << result << endl;
    return 0;
}