Description
Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.
Analysis
对于个位、十位、百位、千位，数字转换成罗马数字的方法都是一样的，用一个transform函数表示即可。
罗马字符 I V X L C D M
整数数字 1 5 10 50 100 500 1000代码：
class Solution {
public:
void transform(string &str, int n, char one, char five, char ten) {
switch (n) {
case 1:
str.push_back(one);
break;
case 2:
str.push_back(one);
str.push_back(one);
break;
case 3:
str.push_back(one);
str.push_back(one);
str.push_back(one);
break;
case 4:
str.push_back(one);
str.push_back(five);
break;
case 5:
str.push_back(five);
break;
case 6:
str.push_back(five);
str.push_back(one);
break;
case 7:
str.push_back(five);
str.push_back(one);
str.push_back(one);
break;
case 8:
str.push_back(five);
str.push_back(one);
str.push_back(one);
str.push_back(one);
break;
case 9:
str.push_back(one);
str.push_back(ten);
break;
case 0:
break;
default:break;
}
}
string intToRoman(int num) {
string result;
int temp = num;
if (temp == 0)
return result;
int thousand = temp / 1000;
temp = temp % 1000;
int hundred = temp / 100;
temp = temp % 100;
int ten = temp / 10;
temp = temp % 10;
int one = temp;
transform(result, thousand, 'M', ' ', ' '); //1000以上的罗马数字字符未知，用空格代替，题目要求只到3999，所以用不到这些字符
transform(result, hundred, 'C', 'D', 'M');
transform(result, ten, 'X', 'L', 'C');
transform(result, one, 'I', 'V', 'X');
return result;
}
};