[Leetcode]-12 Integer to Roman

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.
思路：首先列出罗马数字4000以内的所有整点匹配串（3000-1000，900-100，90-10，9-1）

代码：

class Solution {
public:
string intToRoman(int num) {
string str;
string c [4][10] = {
{"","I","II","III","IV","V","VI","VII","VIII","IX"},
{"","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"},
{"","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"},
{"","M","MM","MMM"}
};
str.append(c[3][num / 1000 % 10]);
str.append(c[2][num / 100 % 10]);
str.append(c[1][num / 10 % 10]);
str.append(c[0][num % 10]);
return str;
}
};