leetcode-12. Integer to Roman

题目：

Given an integer, convert it to a roman numeral.

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

主要思路就是根据10*,90*,50*,40*,这几个点分段处理就行。没有特别需要注意的。

public class Solution {    public String intToRoman(int num) {        StringBuilder sb = new StringBuilder();            if(num>999){                int M = num/1000;                num -= M*1000;                while(M-- !=0){                    sb.append("M");                }            }            if(num > 899){                num -=900;                sb.append("CM");            }            if(num > 499){                num -= 500;                int C = num/100;                num -= C * 100;                sb.append("D");                while(C-- != 0)                    sb.append("C");            }            if(num >399){                num -= 400;                sb.append("CD");            }            if(num > 99){                int C = num/100;                num -= C * 100;                while(C-- != 0)                    sb.append("C");            }            if(num > 89){                num -= 90;                sb.append("XC");            }            if(num > 49){                num -= 50;                sb.append("L");                int X = num/10;                num -= X * 10;                while(X-- != 0){                    sb.append("X");                }            }            if(num > 39){                num -= 40;                sb.append("XL");            }            if(num > 9){                int X = num/10;                num -= X * 10;                while(X-- != 0)                    sb.append("X");            }            if(num > 8){                num -= 9;                sb.append("IX");            }            if(num > 4){                num -= 5;                sb.append("V");                while(num-- != 0)                    sb.append("I");            }            if(num > 3){                num -= 4;                sb.append("IV");            }            if(num > 0){                while(num-- != 0)                sb.append("I");            }        return sb.toString();    }}