leetcode 12. 整数转罗马数字

class Solution
{
public:
    string intToRoman(int num)
    {
        vector vec1 = {"","I","II","III","IV","V","VI","VII","VIII","IX"};
        vector vec2 = {"","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"};
        vector vec3 = {"","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"};
        vector vec4 = {"","M","MM","MMM"};
        return vec4[num/1000]+vec3[(num%1000)/100]+vec2[(num%100)/10]+vec1[num%10];
    }
};