convertToRoman.cpp

#include <iostream>
using namespace std;

// 罗马数字共有 7 个，即 I（1）、V（5）、X（10）、L（50）、C（100）、D（500）和
// M（1000）
string transform(string accu, int n) {
    if (n == 0)
        return accu;

    int ms = n / 1000;
    if (ms > 0)
        return transform(string(ms, 'M'), n - ms * 1000);

    int cs = n / 100;
    if (cs > 0) {
        int r = n - cs * 100;
        if (cs < 4)
            return transform(accu + string(cs, 'C'), r);
        if (cs == 4)
            return transform(accu + "CD", r);
        if (cs < 9)
            return transform(accu + "D" + string(cs - 5, 'C'), r);
        return transform(accu + "CM", r);
    }

    int xs = n / 10;
    if (xs > 0) {
        int r = n - xs * 10;
        if (xs < 4)
            return transform(accu + string(xs, 'X'), r);
        if (xs == 4)
            return transform(accu + "XL", r);
        if (xs < 9)
            return transform(accu + "L" + string(xs - 5, 'X'), r);
        return transform(accu + "XC", r);
    }

    if (n < 4)
        return accu + string(n, 'I');
    if (n == 4)
        return accu + "IV";
    if (n < 9)
        return accu + "V" + string(n - 5, 'I');
    return accu + "IX";
}

void convertToRoman(int n) {
    // Your code here
    cout << transform("", n);
}

int main() {
    for (int i = 1; i < 4000; i++) {
        convertToRoman(i);
        cout << endl;
    }
    return 0;
}