Converting integer to Roman Numeral

Question

I have a test due in about four hours and one of the questions asks us to convert a user-inputed integer up to 100 into a roman numeral. I think my code is very close (I fou

Answer 1

I wrote this for fun; maybe useful. Note however, that it will not work for values greater than 1000. Can adapt it to suit your needs though. Here you go:

enum roman_digits{
    I=1,
    V=5,
    X=10,
    L=50,
    C=100,
    D=500,
    M=1000
};

std::string lookup(roman_digits v) {
    switch (v) {
    case I:
        return "I";
    case V:
        return "V";
    case X:
        return "X";
    case L:
        return "L";
    case C:
        return "C";
    case D:
        return "D";
    case M:
        return "M";
    default:
        return NULL;
    }
}

std::string to_roman(const int value) {
    roman_digits weight[] = { I, V, X, L, C, D, M };
    std::string result;
    int t;
    int i;

    if (value == 0) {
        return NULL;
    } else {
        unsigned int i;
        for (i = 0; i < sizeof(weight) / sizeof(roman_digits); ++i) {
            if (value == weight[i]) {
                return lookup(weight[i]);
            }
        }
    }
    i = 0;
    t = value;
    while (t > 0) {
        t = value;
        t /= weight[i++];
    }
    --i;
    int prev_wt_sub = i % 2 ? (i - 1) : (i - 2);
    if ((weight[i] - weight[prev_wt_sub]) < value) {
        result += lookup(weight[prev_wt_sub]) + lookup(weight[i]) +
                to_roman(value - (weight[i] - weight[prev_wt_sub]));
    } else if ((weight[i] - weight[prev_wt_sub]) > value) {
        prev_wt_sub += (value / weight[prev_wt_sub + 1] ? 1 : 0);
        result += lookup(weight[prev_wt_sub]) +
                to_roman(value - weight[prev_wt_sub]);
    } else {
        result += lookup(weight[prev_wt_sub]) + lookup(weight[i]);
    }

    return result;
}