leetcode RomanToInt

class Solution {public://罗马数字规律问题求解，寻找加减规律//当前字符与前一字符代表的value,关系为解题关键//罗马字符表如上图所示int romanToInt(string s) {int length = s.size();    map<char, int> roman;    int res;    roman['I'] = 1;    roman['V'] = 5;    roman['X'] = 10;    roman['L'] = 50;    roman['C'] = 100;    roman['D'] = 500;    roman['M'] = 1000;    res = roman[s[length -1]];    for(int j = length - 2 ; j>=0 ; j--){        if(roman[s[j]] >= roman[s[j+1]]){            res = res + roman[s[j]];        }        else{            res = res - roman[s[j]];        }    }    return res;}};