Leetcode 153. Find Minimum in Rotated Sorted Array -- 二分查找的变种

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).

Find the minimum element.

You may assume no duplicate exists in the array.

 

 

 class Solution {  
public:  
    int findMin(vector<int> &num) {  
        int start = 0;  
        int end = num.size() - 1;  
        int mid = 0;  
        while (start < end) { //注意这里和普通的二分查找不同，这里是start < end不是 start <= end.  
                mid = start + (end - start)/2;  
                if (num[mid] > num[end])  
                    start = mid + 1; //此时可以扔掉mid的值  
                else   
                    end = mid;//此时不能扔掉mid的值  
        }  
        return num[end]; //退出循环说明start与end相等，所以只剩一个元素可能，所以return [start]或者return [end]都可以了。  
        //注意不能return mid，可以从{2,1}这个输入看出来。  
          
    }  
};