【leetcode】500. Keyboard Row

問題描述：

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.

 

 

Example 1:

Input: ["Hello", "Alaska", "Dad", "Peace"]
Output: ["Alaska", "Dad"]

 

Note:

1. You may use one character in the keyboard more than once.
2. You may assume the input string will only contain letters of alphabet.

解法一：

常規解法，用unordered_set存儲每一行的字母，依次尋找判斷。

 1 class Solution {
 2 public:
 3     vector<string> findWords(vector<string>& words) {
 4        unordered_set<char> row1 {'q', 'w', 'e', 'r', 't', 'y','u', 'i', 'o', 'p'};
 5         unordered_set<char> row2 {'a', 's', 'd', 'f', 'g', 'h', 'j', 'k', 'l'}; 
 6         unordered_set<char> row3 { 'z', 'x', 'c', 'v', 'b' ,'n', 'm'};
 7         vector<unordered_set<char>> rows {row1, row2, row3};
 8         
 9         
10         vector<string> validWords;
11         for(int i=0; i<words.size(); ++i){
12             int row=0;
13             
14             for(int k=0; k<3; ++k){
15                 if(rows[k].count((char)tolower(words[i][0])) > 0) row = k;
16             }
17             
18             validWords.push_back(words[i]);
19             for(int j=1; j<words[i].size(); ++j){
20                 if(rows[row].count((char)tolower(words[i][j])) == 0){
21                     validWords.pop_back();
22                     break;
23                 }
24             }
25             
26         }
27         return validWords;
28     }
29 };

解法二：

這種解法比較有啓發性，看起來頗有意思。

 1 class Solution {
 2 public:
 4 vector<string> findWords(vector<string>& words) 
 5 {
 6     vector<string> res;
 7     
 8     for(auto str : words)
 9     {
10         bool r1 = str.find_first_of("QWERTYUIOPqwertyuiop") == string::npos ? false : true;
11         bool r2 = str.find_first_of("ASDFGHJKLasdfghjkl") == string::npos ? false : true;
12         bool r3 = str.find_first_of("ZXCVBNMzxcvbnm") == string::npos ? false : true;
13         
14         if(r1 + r2 + r3 == 1)
15             res.push_back(str);
16     }
17     
18     return res;
19 }
20     
21 };