Roman_to_int.cpp

#include <iostream>
using namespace std;
int value(char roman)
{
    switch (roman)
    {
    case 'I': return 1;
    case 'V': return 5;
    case 'X': return 10;
    case 'L': return 50;
    case 'C': return 100;
    case 'D': return 500;
    case 'M': return 1000;
    }
}
int romanToInt (string A)
{
    int i, n, ans = 0, p = 0;
    n = A.length() - 1;

    for ( i = n; i >= 0; i--)
    {
        if ( value(A[i]) >= p)
            ans = ans + value(A[i]);
        else
            ans = ans - value(A[i]);

        p = value(A[i]);
    }
    return ans;
}

//Main Function
int main() {

    string s;
    int num;
    cin >> s;
    num = romanToInt(s);
    cout << num << "\n";
    return 0;
}