将 1~3999 内的整数正确转换至罗马数字

roman.cc

#include <algorithm>
#include <cassert>
#include <string>

std::string toRoman(int number)
{
    static struct {
        int value;
        char const *symbols;
    } const mapping[] = {
        { 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"  },
    };
    
    assert(number > 0);
    
    std::string roman;
    
    for (auto iter = std::begin(mapping);
         iter != std::end(mapping) && number > 0;
         ++iter)
    {
        int count = number / iter->value;
        number    = number % iter->value;
        for (int i = 0; i< count; i++) {
            roman.append(iter->symbols);
        }
    }
    
    return roman;
}