Roman Numeral in C++

Welcome to the Roman Numeral in C++ page! Here, you’ll find the source code for this program as well as a description of how the program works.

Current Solution

#include <iostream>
#include <bits/stdc++.h>

using namespace std;

bool is_roman(char x)
{
    return !(x == 'I' || x == 'V' || x == 'X' || x == 'L' || x == 'C' || x == 'D' || x == 'M');
}

int main(int argc, char *argv[])
{
    if (argv[1] == NULL)
    {
        cerr << "Usage: please provide a string of roman numerals" << endl;
        exit(0);
    }

    string s;
    s = argv[1];

    for (char c : s)
    {
        if (is_roman(c))
        {
            cerr << "Error: invalid string of roman numerals" << endl;
            exit(0);
        }
    }

    map<char, int> value;
    value['I'] = 1;
    value['V'] = 5;
    value['X'] = 10;
    value['L'] = 50;
    value['C'] = 100;
    value['D'] = 500;
    value['M'] = 1000;

    int num = 0;

    for (int i = s.size() - 1; i >= 0; i--)
    {
        if (value[s[i]] > value[s[i - 1]] && i > 0)
        {
            num += value[s[i]] - value[s[i - 1]];
            i--;
        }
        else
        {
            num += value[s[i]];
        }
    }

    cout << num << endl;
}

Roman Numeral in C++ was written by:

• Jeremy Grifski
• Sailok Chinta

If you see anything you’d like to change or update, please consider contributing.

Note: The solution shown above is the current solution in the Sample Programs repository as of Oct 10 2022 16:05:09. The solution was first committed on Oct 21 2019 18:38:06. As a result, documentation below may be outdated.

How to Implement the Solution

No ‘How to Implement the Solution’ section available. Please consider contributing.

How to Run the Solution

No ‘How to Run the Solution’ section available. Please consider contributing.