500. Keyboard Row-键盘行

Given an array of strings words, return the words that can be typed using letters of the alphabet on only one row of American keyboard like the image below.

In the American keyboard:

• the first row consists of the characters "qwertyuiop",
• the second row consists of the characters "asdfghjkl", and
• the third row consists of the characters "zxcvbnm".

Example 1:
Input: words = ["Hello","Alaska","Dad","Peace"]
Output: ["Alaska","Dad"]

Example 2:
Input: words = ["omk"]
Output: []

Example 3:
Input: words = ["adsdf","sfd"]
Output: ["adsdf","sfd"]

Constraints:

• 1 <= words.length <= 20
• 1 <= words[i].length <= 100
• words[i] consists of English letters (both lowercase and uppercase). 

Solution in python:

class Solution:
    def findWords(self, words: List[str]) -> List[str]:
        set1 = set("qwertyuiop")
        set2 = set("asdfghjkl")
        set3 = set("zxcvbnm")
        sets = [set1, set2, set3]
        result = []
        for item in words:
            index = None
            for i in range(len(sets)):
                if (item[0]).lower() in sets[i]:
                    index = i
            flag = True
            for char in item:
                if (char).lower() not in sets[index]:
                    flag = False
                    break
            if flag:
                result.append(item)
        return result