题目

roman-to-integer

算法

o(n)

代码

class Solution{

public:

    int romanToInt(string s){

        int res=0;

        unordered_map<char,int> m{{'I',1},{'V',5},{'X',10},{'L',50},{'C',100},{'D',500},{'M',1000}};

        for(int i=0;i<s.size();++i){

            int val=m[s[i]];

            if(i==s.size()-1 || m[s[i+1]]<=m[s[i]])  res+=val;

            else res-=val;

        }



        return res;

    }

};