From f62b9e251a55f97d262adf28312eeb777d7029ee 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, 4 Sep 2018 21:47:00 +0800
Subject: [PATCH] Create 189. Rotate Array.md

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+# [189. Rotate Array](https://leetcode.com/problems/rotate-array/description/)
+# 思路
+题意就是循环右移k步，如果仔细观察结果可知，结果相当于先对数组整体进行翻转，再对前k个元素和后面的元素分别进行翻转的结果。  
+例如[1,2,3,4,5,6,7], k = 3:  
+先整体翻转:[7,6,5,4,3,2,1];  
+再对前3个元素翻转:[5,6,7,4,3,2,1];  
+再对后面的元素翻转:【5,6,7,1,2,3,4]。   
+时间复杂度O(n), 空间复杂度O(1)。
+# C++
+```
+class Solution {
+public:
+    void rotate(vector<int>& nums, int k) {
+        k %= nums.size(); // 注意先取模
+        if(k == 0) return;
+        reverse(nums.begin(), nums.end());
+        reverse(nums.begin(), nums.begin() + k);
+        reverse(nums.begin() + k, nums.end());       
+    }
+};
+```