[leetcode]33. 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.

分析：二分法查找，注意临界情况。

代码：

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