017. Integer to Roman/solution.h

#include <string>
#include <unordered_map>
using std::string;

class Solution {
public:
    string intToRoman(int num) {
        std::map<int, string> map = {{1000, "M"}, {900, "CM"}, {500, "D"}, {400, "CD"}, {100, "C"}, 
                                     {90, "XC"}, {50, "L"}, {40, "XL"}, {10, "X"}, {9, "IX"}, {5, "V"}, {4, "IV"}, {1, "I"}};
        string ret;
        for (auto iter = map.rbegin(); iter != map.rend(); ++iter)
            while (num >= iter->first)
            {
                ret += map[iter->first];
                num -= iter->first;
            }
        return ret;
    }
};