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;
    }
};