【leetcode】Roman to Integer

 1 class Solution {
 2 public:
 3     int romanToInt(string s) {
 4         map<char,int> hash;
 5         hash[‘I‘] = 1;  
 6         hash[‘V‘] = 5;  
 7         hash[‘X‘] = 10;  
 8         hash[‘L‘] = 50;  
 9         hash[‘C‘] = 100;  
10         hash[‘D‘] = 500;  
11         hash[‘M‘] = 1000;
12        
13         int result=hash[s[0]];
14         for(int i=1;i<s.length();i++)
15         {
16             int pre=hash[s[i-1]];
17             int cur=hash[s[i]];
18             if(pre>=cur)
19             {
20                 result+=cur;
21             }
22             else
23             {
24                 result+=cur-2*pre;
25             }
26            
27         }
28         return result;
29     }
30 };