33. 搜索旋转排序数组 Search in Rotated Sorted Array

You are given an integer array nums sorted in ascending order, and an integer target.

Suppose that nums 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]).

If target is found in the array return its index, otherwise, return -1.

 

Input: nums = [4,5,6,7,0,1,2], target = 0
Output: 4

方法：

二分查找，利用至少有一半是递增数列。 

 

public int search(int[] nums, int target) {
        int l = 0, r = nums.length - 1;
        while( l <= r ){
            int mid = l + (r - l)/2;
            if( nums[mid] == target) return mid;
            if(nums[l] <= nums[mid]){
                if(nums[l] <= target && nums[mid] > target){
                    r = mid - 1;
                }else l = mid + 1;
            }else{
                if( nums[mid] < target && nums[r] >= target){
                    l = mid + 1;
                }else r = mid - 1;
            }
        }
        return -1;
    }

 

参考链接：

https://leetcode.com/problems/search-in-rotated-sorted-array/

https://leetcode-cn.com/problems/search-in-rotated-sorted-array/