LeetCode 500. Keyboard Row （键盘行）

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.

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题目标签：Hash Table

　　题目给了我们一个words array，让我们判断每一个word 中的 chars 是否都来自于键盘上的同一行。

　　利用HashMap 把键盘上的3行 chars 保存：char 当作 key；行数 当作 value。

　　接着遍历words，检查每一个word。

Java Solution:

Runtime beats 68.36% 

完成日期：06/07/2017

关键词：HashMap

关键点：char 当作 key；行数 当作 value

class Solution 
{
    public String[] findWords(String[] words) 
    {
        HashMap<Character, Integer> map = new HashMap<>();
        List<String> resList = new ArrayList<>();
        
        String row1 = "qwertyuiop";
        String row2 = "asdfghjkl";
        String row3 = "zxcvbnm";
        
        // set up the map
        for(char c: row1.toCharArray())
            map.put(c, 1);
        
        for(char c: row2.toCharArray())
            map.put(c, 2);
        
        for(char c: row3.toCharArray())
            map.put(c, 3);
        
        
        // iterate each word to check all chars are from one row
        for(String word: words)
        {
            char[] wordChars = word.toLowerCase().toCharArray();
            int rowNumber = map.get(wordChars[0]);
            boolean add = true;
            
            for(char c: wordChars)
            {
                if(rowNumber != map.get(c))
                {
                    add = false;
                    break;
                }
                   
            }
            
            if(add)
                resList.add(word);
        }
        
        String[] res = new String[resList.size()];
        
        for(int i=0; i<res.length; i++)
            res[i] = resList.get(i);
        
        return res;
    }
}

参考资料：N/A　　

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