Integer to Roman

https://leetcode.com/problems/integer-to-roman/description/

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

Thoughts

本质上是不断除10, 把每一位映射回去. 只是千, 百, 十都有各自的映射.

Code

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

Analysis

时空复杂度O(1).