Roman to Integer

问题：罗马数字变为整数

class Solution {
public:
    int romanToInt(string s) {
         char c[10][10][10]={{"0","I","II","III","IV","V","VI","VII","VIII","IX"},{"0","X","XX","XXX","XL","L","LX"
        ,"LXX","LXXX","XC"},{"0","C","CC","CCC","CD","D",
              "DC","DCC","DCCC","CM"},{"0","M","MM","MMM"}};
         int num=0,i;
         for(i=0;i<s.size();i++)
         {
             if(s[i]=='I') num+=1;
             if(s[i]=='V') 
             {
                if(i!=0 && s[i-1]=='I') num+=3;
                else num+=5;
             }
             if(s[i]=='X')
             {
                 if(i!=0 && s[i-1]=='I') num+=8;
                 else num+=10;
             }
             if(s[i]=='L')
             {
                 if(i!=0 && s[i-1]=='X') num+=30;
                 else num+=50;
             }
             if(s[i]=='C')
             {
                 if(i!=0 && s[i-1]=='X') num+=80;
                 else num+=100;
             }
             if(s[i]=='D')
             {
                 if(i!=0 && s[i-1]=='C') num+=300;
                 else num+=500;
             }
             if(s[i]=='M')  
             {
                 if(i!=0 && s[i-1]=='C') num+=800;
                 else num+=1000;
             }
         }
         return num;
    }
};