500. Keyboard Row

一、题目：

Given a List of words, return the words that can be typed using letters of alphabet on only one row's of American keyboard like the image below.

二、解题

class Solution {    /*    从第一个单词开始找，先找出该单词首字母在哪行，    然后看那个单词是否都在那行。    若在，给添加到result中。    */public:    vector<string> findWords(vector<string>& words) {        unordered_set<char> row1{ 'q', 'w', 'e', 'r', 't', 'y','u', 'i', 'o', 'p' };        unordered_set<char> row2{ 'a', 's', 'd', 'f', 'g', 'h', 'j', 'k', 'l' };        unordered_set<char> row3{ 'z', 'x', 'c', 'v', 'b' ,'n', 'm' };        vector<unordered_set<char>> rows{ row1, row2, row3 };        vector<string> validWords;        for (int i = 0; i<words.size(); ++i) {            int row = 0;            for (int k = 0; k<3; ++k) {                if (rows[k].count((char)tolower(words[i][0])) > 0) row = k;            }            for (int j = 0; j<words[i].size(); ++j) {                if (rows[row].count((char)tolower(words[i][j])) == 0)                    break;                if (j == words[i].size() - 1)                    validWords.push_back(words[i]);            }        }        return validWords;    }};