roman numbers value

t11e25.rom2int.cpp

// t11e25.rom2int.cpp
// juanfc 2023-11-22
// https://gist.github.com/f47e281ad205395051fd1aaf8f0aa13a

#include <iostream>
using namespace std;

void test(string s);

int main()
{
    test("iIi");
    test("iv");
    test("liv");
    return 0;
}

int rom2int(string s);

void test(string s)
{
    cout << s << " = " << rom2int(s) << endl;
}

int value(char c);
void tolow(string& s);
int rom2int(string s)
{
    tolow(s);
    int r = 0;
    int prev = 0;
    for (int i = s.length()-1; i >= 0; --i) {
        int v = value(s[i]);
        if (v < prev)
            r -= v;
        else
            r += v;
        prev = v;
    }
    return r;
}
int value(char c)
{
    int r = 0;
    switch (c) {
        case 'i': r = 1; break;
        case 'v': r = 5; break;
        case 'x': r = 10; break;
        case 'l': r = 50; break;
        case 'c': r = 100; break;
        case 'd': r = 500; break;
        case 'm': r = 1000; break;
    }
    return r;
}

void tolow(string& s)
{
    for (int i = 0; i < s.length(); ++i)
        s[i] = tolower(s[i]);
}

char tolower(char c)
{
    return ('A' <= c and c <= 'Z')? c+'a'-'A' : c;
}