Roman to Integer

Given a roman numeral, convert it to an integer.
Input is guaranteed to be within the range from 1 to 3999.

我们做过Integer to Roman 这道题目，在里面讲了罗马数字的规则，这道题是罗马数字转整数，不明白规则的看一下上一道题目，代码如下：

public class Solution {
    public int romanToInt(String s) {
        int result = 0;
        int next = 0;
        for(int i = s.length() - 1; i >= 0; i--)
            switch(s.charAt(i)) {
                case 'I':
                    if(next > 1)
                        result -= 1;
                    else
                        result += 1;
                   next = 1;
                   break;
                   
                case 'V':
                    if(next > 5)
                        result -= 5;
                    else
                        result += 5;
                   next = 5;
                   break;
                   
                case 'X':
                    if(next > 10)
                        result -= 10;
                    else
                        result += 10;
                   next = 10;
                   break;
                   
                 case 'L':
                    if(next > 50)
                        result -= 50;
                    else
                        result += 50;
                   next = 50;
                   break;
                   
                 case 'C':
                    if(next > 100)
                        result -= 100;
                    else
                        result += 100;
                   next = 100;
                   break;
                   
                 case 'D':
                    if(next > 500)
                        result -= 500;
                    else
                        result += 500;
                   next = 500;
                   break;
                   
                 case 'M':
                    if(next > 1000)
                        result -= 1000;
                    else
                        result += 1000;
                   next = 1000;
                   break;
            }
        return result;
    }
}