It's only a little trick. Just for fun.

```
public int romanToInt(String s) {
// I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000
Character[] roman = {'I', 'V', 'X', 'L', 'C', 'D', 'M'};
int[] number = {1, 5, 10, 50, 100, 500, 1000};
int ret = 0, old = 0;
for(int i = s.length() - 1; i >= 0; i --){
Character temp = s.charAt(i);
for(int j = 0; j < roman.length; j ++){
if(temp == roman[j]){
if(number[j] >= old)
ret += number[j];
else
ret -= number[j];
old = number[j];
}
}
}
return ret;
}
```