[leetcode] 500. Keyboard Row

最新推荐文章于 2021-01-24 22:56:51 发布

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#Hash Table

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本文介绍了一个简单的算法问题，即如何找出能用美国键盘同一行字母组成的单词。通过使用哈希表存储不同行的字母，该解决方案能够高效地检查每个单词是否符合要求。

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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.

这道题是判断单词能否由键盘某一行中字母组合而成，题目难度为Easy。

题目比较简单，将各行字母分别存入Hash Table中，然后逐个判断数组中字符串即可。具体代码：

class Solution {
public:
    vector<string> findWords(vector<string>& words) {
        vector<string> ret;
        unordered_map<char, int> hash;
        
        hash['Q'] = hash['q'] = 1;
        hash['W'] = hash['w'] = 1;
        hash['E'] = hash['e'] = 1;
        hash['R'] = hash['r'] = 1;
        hash['T'] = hash['t'] = 1;
        hash['Y'] = hash['y'] = 1;
        hash['U'] = hash['u'] = 1;
        hash['I'] = hash['i'] = 1;
        hash['O'] = hash['o'] = 1;
        hash['P'] = hash['p'] = 1;
        hash['A'] = hash['a'] = 2;
        hash['S'] = hash['s'] = 2;
        hash['D'] = hash['d'] = 2;
        hash['F'] = hash['f'] = 2;
        hash['G'] = hash['g'] = 2;
        hash['H'] = hash['h'] = 2;
        hash['J'] = hash['j'] = 2;
        hash['K'] = hash['k'] = 2;
        hash['L'] = hash['l'] = 2;
        hash['Z'] = hash['z'] = 3;
        hash['X'] = hash['x'] = 3;
        hash['C'] = hash['c'] = 3;
        hash['V'] = hash['v'] = 3;
        hash['B'] = hash['b'] = 3;
        hash['N'] = hash['n'] = 3;
        hash['M'] = hash['m'] = 3;
        
        for(auto s:words) {
            int row = hash[s[0]];
            bool inOneRow = true;
            for(auto c:s) {
                if(hash[c] != row) {
                    inOneRow = false;
                    break;
                }
            }
            if(inOneRow) ret.push_back(s);
        }
        
        return ret;
    }
};