Leetcode102: Search in Rotated Sorted Array

Suppose a sorted array 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.

如果中间元素大于首部元素，那么表明查找区间左半部分是有序的，然后再根据target是否在有序的一部分来决定接下来查找的方向

如果中间元素小于首部元素，那么查找区间有半部分是有序的，然后再根据target是否在有序的一部分来决定接下来查找的方向

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