500. Keyboard Row（判断单词能否由键盘上的某一行字符表示）-蒲公英云

500. Keyboard Row（判断单词能否由键盘上的某一行字符表示）

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.

American keyboard

Example 1:

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

Note:

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

题目大意：给定一组字符串，判断其中哪些可以由键盘上的某一行字母表示，输出满足条件的字符串所构成的字符串数组。

解题思路：定义一个长度为26的整型数组keyboard，keyboard[i]表示字符‘a’+1属于键盘上的第几行字母（第一行，第二行，或者第三行）。对每一个字符串进行判断，如果每一个字符都在同一行，则该字符串满足条件，否则不满足。

代码如下：（3ms，beats 82.87%）

public String[] findWords(String[] words) {
        int[] keyboard = new int[] { 2, 3, 3, 2, 1, 2, 2, 2, 1, 2, 2, 2, 3, 3, 1, 1, 1, 1, 2, 1, 1, 3, 1, 3, 1, 3 };
        String[] temp = new String[words.length];
        int index = 0;
        for (String word : words) {
            char[] chars = word.toLowerCase().toCharArray();
            int len = chars.length;
            if (len == 0)
                break;
            int row = keyboard[chars[0] - 'a'];
            int i;
            for (i = 0; i < len; i++) {
                if (keyboard[chars[i] - 'a'] != row)
                    break;
            }
            if (i == len)
                temp[index++] = word;
        }
        String[] res = new String[index];
        for(int i=0;i<index;i++)
            res[i] = temp[i];
        return res;
    }