Recover Rotated Sorted Array

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

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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]




思路是三次反转数组，第一次反转以后用一个o(n)时间找到要反转的点，然后再对index的左右两侧进行两次反转。

代码：

public void recoverRotatedSortedArray(ArrayList<Integer> nums) {        // write your code        if(nums == null || nums.size() == 0) return;        Collections.reverse(nums);        int index= -1;        for(int i=0;i<nums.size()-1;i++){            if(nums.get(i)<nums.get(i+1)){                //i is the place where need to split                index = i;                break;            }        }        if(index != nums.size()){            //Collcetions.reverse()            reverse(nums, 0, index);            reverse(nums, index+1, nums.size()-1);        }else{            Collections.reverse(nums);        }    }        private void reverse(ArrayList<Integer> nums, int i, int j){        while(i<j){            int temp = nums.get(i);            nums.set(i, nums.get(j));            nums.set(j, temp);            i++;j--;        }    }