13.Roman to Integer

   /*
    * 13.Roman to Integer
    * 2016-4-14 by Mingyang
    * 注意几个特殊点就好了
    */
     public static int romanToInt(String s) {
            int res=0;
            if(s==null||s.length()==0)
              return res;
            for(int i=0;i<s.length();i++){
                char temp=s.charAt(i);
                if(temp=='V'){
                    res=res+5;
                }else if(temp=='L'){
                    res=res+50;
                }else if(temp=='D'){
                    res=res+500;
                }else if(temp=='I'){
                    if(i!=s.length()-1&&(s.charAt(i+1)=='V'||s.charAt(i+1)=='X')){
                        res=res-1;
                    }else{
                        res=res+1;
                    }
                }else if(temp=='X'){
                    if(i!=s.length()-1&&(s.charAt(i+1)=='L'||s.charAt(i+1)=='C')){
                        res=res-10;
                    }else{
                        res=res+10;
                    }
                }else if(temp=='C'){
                    if(i!=s.length()-1&&(s.charAt(i+1)=='D'||s.charAt(i+1)=='M')){
                        res=res-100;
                    }else{
                        res=res+100;
                    }
                }else if(temp=='M'){
                    res=res+1000;
                }
            }
            return res;
        }