Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.
[0,1,2,4,5,6,7] might become
You are given a target value to search. If found in the array return its index, otherwise return -1.
You may assume no duplicate exists in the array.
Your algorithm’s runtime complexity must be in the order of O(log n).
Input: nums = [4,5,6,7,0,1,2], target = 0
Input: nums = [4,5,6,7,0,1,2], target = 3
不过此题是Rotated Sorted Array，所以不能通过mid与左右指针指向的值的比较来移动指针。而是通过判断哪一部分是有序的，target是否在这个有序的部分来实现。