Roman to Integer

 1 class Solution {
 2 public:
 3     int romanToInt(string s) {
 4         char temp;
 5         int leng=s.length();
 6         if(leng==0)
 7             return 0;
 8         int res=charToInt(s.at(leng-1));
 9         for(int i=leng-2;i>=0;i--){
10             temp=s.at(i);
11             int number=charToInt(temp);
12             if(charToInt(s.at(i))<charToInt(s.at(i+1)))
13                 res-=charToInt(s.at(i));
14             else
15                 res+=charToInt(s.at(i));
16         }
17         return res;
18         
19     }
20     int charToInt(char c)
21     {
22         int num=0;
23         switch(c)
24         {
25             case 'I':num=1;
26             break;
27             case 'V':num=5;
28             break;
29             case 'X':num=10;
30             break;
31             case 'L':num=50;
32             break;
33             case 'C':num=100;
34             break;
35             case 'D':num=500;
36             break;
37             case 'M':num=1000;
38             break;
39         }
40         return num;
41     }
42 };