Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

class Solution {
public:
    int map(char c)  
    {  
        switch(c)  
        {  
            case 'I':  
                return 1;  
            case 'V':  
                return 5;  
            case 'X':  
                return 10;  
            case 'L':  
                return 50;  
            case 'C':  
                return 100;  
            case 'D':  
                return 500;  
            case 'M':  
                return 1000;  
            default:  
                return 0;  
        }  
    } 
    
    int romanToInt(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int nSize = s.size();
        int pre = 1001;
        int result = 0;
        int cur;
        for (int i = 0; i < nSize; ++i)
        {
            cur = map(s[i]);
            result += cur;
            if (cur > pre)
            {
                result -= 2*pre;
            }
            pre = cur;
        }
        return result;
    }
};