#39 Recover Rotated Sorted Array

题目描述：

Given a rotated sorted array, recover it to sorted array in-place.

Have you met this question in a real interview? 

Yes

Clarification

What is rotated array?

• For example, the orginal array is [1,2,3,4], The rotated array of it can be [1,2,3,4], [2,3,4,1], [3,4,1,2], [4,1,2,3]

Example

[4, 5, 1, 2, 3] -> [1, 2, 3, 4, 5]

Challenge 

In-place, O(1) extra space and O(n) time.

题目思路：

看到这题真是傻眼了很久，一直想的是怎么一个一个去in-place。。。这个array不顺(不是in order）但是可以分成顺的两截：一截从小到大，一截从小到大。那么如果把这两截分别reverse，这俩就顺利的接起来了。再整体reverse一下就是答案了！

Mycode（AC = 17ms）：

</pre><pre name="code" class="cpp">class Solution {public:    void recoverRotatedSortedArray(vector<int> &nums) {        // write your code here        if (nums.size() <= 1) return;                for (int i = 0; i < nums.size() - 1; i++) {            if (nums[i] > nums[i + 1]) {                // 4,5,1,2,3 -> 4,5,3,2,1                reverse(nums.begin() + i + 1, nums.end());                // 4,5,3,2,1 -> 5,4,3,2,1                reverse(nums.begin(), nums.begin() + i + 1);                // 5,4,3,2,1 -> 1,2,3,4,5                reverse(nums.begin(), nums.end());                return;            }        }                return;    }    };