【LeetCode】012.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.
解答：
从千位到个位，根据位数不同选择不同的字母，char1,char5,char10分别代表该位表示1，5和10的字母。

c为当前位数字（0---9），模式为：

c -- 9 char1 + char10

c :5 ---8 char5 + char1[c-5]

c:4 char1+char5

c:1--3 char1[c]

代码：

public class Solution {
public String intToRoman(int num) {
StringBuilder str = new StringBuilder();
char[] chars;
char char1 = 0, char5=0,char10=0;
int mode = 1000;
while (mode > 0) {
int c = num / mode;
num %= mode;
switch (mode) {
case 1000:
char1 = 'M';
if(c > 3)
return "error";
break;
case 100:
char1 = 'C';
char5 = 'D';
char10 = 'M';
break;
case 10:
char1 = 'X';
char5 = 'L';
char10 = 'C';
break;
case 1:
char1 = 'I';
char5 = 'V';
char10 = 'X';
break;
default:
break;
}
if (c == 9)
str.append(char1).append(char10);
else if (c >= 5) { // 5 --- 8
chars = new char[c - 5 + 1];
Arrays.fill(chars, char1);
chars[0] = char5;
str.append(chars);
} else if (c == 4) // 4
str.append(char1).append(char5);
else if(c > 0){ // 1 --- 3
chars = new char[c];
Arrays.fill(chars, char1);
str.append(chars);
}
mode /= 10;
}
return str.toString();
}
}