题解 | #第一个只出现一次的字符#

class Solution {
public:
    int FirstNotRepeatingChar(string str) {
        map<int, int> mp;
        int res = -1;
        for(int i = 0; i < str.size(); i++) {
            auto c = str[i] - 'a';
            mp[c] ++;
        }
        for(int i = 0; i < str.size(); i++) {
            auto c = str[i] - 'a';
            if(mp[c] == 1){
                res = i;
                break;
            }
                
        }
        return res;
    }
};