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 val(char s)    {        switch (s)         {            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;        }    }    int romanToInt(string s) {        if(s[0]==NULL) return 0;        char q=s[0],t=s[1];        int sum=0,i=1;        while(t!=NULL)        {            if(val(q)>=val(t)) sum=sum+val(q);            else sum=sum-val(q);            q=s[i];            t=s[i+1];            i++;        }        sum=sum+val(q);        return sum;    }};