Анализатор Арифметических выражений V2.1

#include <iostream>
#include <string>

using namespace std;


void pro_del(string &s)
{
    for (int i = 0; i < s.size(); i++)
    {
        if (s[i] == ' ') { s.erase(i, 1); i--; };
    }
}

string NO_SKOBKI(string s)
{
    for (int i = 0; i < s.size(); i++)
    {
        if (s[i] == ')' || s[i] == '(') { s.erase(i, 1); i--; };
    }
    return s;
}


int str_in_int(string s)
{
    int count = 1;
    int res = 0;
    for (int i = s.size() - 1; i >= 0; i--)
    {
        if (s[i] >= '0' && s[i] <= '9')
        {
            res = res + (s[i] - '0')*count;
            count*=10;
        }
    }
    return res;
}

int power_of_God(string s)
{
    //cout << s << endl;
    if (s.find_first_of("+-*") == string::npos) return str_in_int(s);
    int pr = 0;
    while (true)
    {
        int c = 0;
        for (int i = s.size() - 1; i >= 0; i--)
        {
            if (s[i] == ')') c++; else if (s[i] == '(') c--;
            if (c == pr && s[i] == '+') return power_of_God(s.substr(0, i)) + power_of_God(s.substr(i + 1));
        }
        c = 0;
        for (int i = s.size() - 1; i >= 0; i--)
        {
            if (s[i] == ')') c++; else if (s[i] == '(') c--;
            if (c == pr && s[i] == '-') return power_of_God(s.substr(0, i)) - power_of_God(s.substr(i + 1));
        }
        c = 0;
        for (int i = s.size() - 1; i >= 0; i--)
        {
            if (s[i] == ')') c++; else if (s[i] == '(') c--;
            if (c == pr && s[i] == '*') return power_of_God(s.substr(0, i)) * power_of_God(s.substr(i + 1));
        }
        pr++;
    }
}


int main()
{
    string s1;
    cin >> s1;
    //if (power_of_God(s1) == power_of_God(NO_SKOBKI(s1))) cout << 1; else cout << 0;
    cout << power_of_God(s1);
    system("pause");
    return 0;
}