500. 键盘行

给定一个单词列表，只返回可以使用在键盘同一行的字母打印出来的单词。键盘如下图所示。

示例1:

输入: ["Hello", "Alaska", "Dad", "Peace"]
输出: ["Alaska", "Dad"]

注意:

1. 你可以重复使用键盘上同一字符。
2. 你可以假设输入的字符串将只包含字母。

收获：

std::unordered_set

http://classfoo.com/ccby/article/qNNOJ

class Solution {
public:
    vector<string> findWords(vector<string>& words) {
        vector<string> res;
        unordered_set<char> row1 {'q','w','e','r','t','y','u','i','o','p','Q','W','E','R','T','Y','U','I','O','P'};
        unordered_set<char> row2{'a','s','d','f','g','h','j','k','l','A','S','D','F','G','H','J','K','L'};
        unordered_set<char> row3{'z','x','c','v','b','n','m','Z','X','C','V','B','N','M'};
        for(string word : words) {
            int a = 0;
            int b = 0;
            int c = 0;
            for(char ch : word) {
                if(row1.count(ch)) a = 1;
                else if(row2.count(ch)) b = 1;
                else if(row3.count(ch)) c = 1;
                
                if(a + b + c > 1) break;    
            }
            if(a + b + c == 1) res.push_back(word);
        }
        
        return res;
    }
};