From 3286d7a8d48198a1875450fe894f7cb52ef5d422 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=94=90=E6=A0=91=E6=A3=AE?= <14021051@buaa.edu.cn>
Date: Tue, 18 Sep 2018 23:47:15 +0800
Subject: [PATCH] Create 500. Keyboard Row.md

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 500. Keyboard Row.md | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 500. Keyboard Row.md

diff --git a/500. Keyboard Row.md b/500. Keyboard Row.md
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+# [500. Keyboard Row](https://leetcode.com/problems/keyboard-row/description/)
+# 思路
+题目意思就是给定一个字符串，若字符串中的每个字母来自键盘上的同一行，则输出。  
+我们可以将字母按照键盘布局分类，从上到下分别为0、1、2类。对于每个字符串，遍历一遍，若属于同一类则可输出。  
+时间复杂度O(n)
+# C++
+```
+class Solution {
+private:
+    int count_hash_index(char c){
+        if(c >= 'a' && c <= 'z') return int(c - 'a');
+        return int(c - 'A');
+    }
+public:
+    vector<string> findWords(vector<string>& words) {
+        //              a b c d e f g h i j k l m n o p q r s t u v w x y z
+        int hash[26] = {1,2,2,1,0,1,1,1,0,1,1,1,2,2,0,0,0,0,1,0,0,2,0,2,0,2};
+        vector<string>res;
+        int i;
+        for(string str: words){
+            for(i = 1; i < str.size(); i++){
+                if(hash[count_hash_index(str[i])] != hash[count_hash_index(str[i - 1])]) break;
+            }
+            if(i == str.size()) res.push_back(str); // 正常退出，则所有字母属于同类
+        }
+        return res;
+    }
+};
+```