https://leetcode.com/problems/search-in-rotated-sorted-array/description/
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.
(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).
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.
time: o(logn) space: o(1)
1 public int search(int[] nums, int target) {
2 if (nums == null || nums.length ==0 ) return -1 ;
3 int left = 0, right = nums.length -1 ;
4 while(left + 1 < right){
5 int mid = left + (right-left)/2;
6 if (nums[mid] == target) return mid ;
7 //break into two parts: note, there is no duplicate
8 //first half
9 if (nums[left]< nums[mid] ){
10 if (target<=nums[mid] && nums[left] <=target){
11 right = mid ;
12 }else {
13 left = mid ;
14 }
15 }
16 //second half: 注意判断顺序变化： 考虑单调的，避开非单调的！
17 else {
18 if (nums[mid]<=target && target <= nums[right]){
19 left = mid ;
20 }else {
21 right = mid;
22 }
23 }
24 }
25 //post processing for the left and right
26 if (nums[left] == target){
27 return left ;
28 }
29 if(nums[right] == target){
30 return right;
31 }
32 return -1 ;
33 }
