153. Find Minimum 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).

Find the minimum element.

You may assume no duplicate exists in the array.

二分法

class Solution {
public:
    int findMin(vector<int>& nums) {
        int lb = 0;
        int ub = nums.size() - 1;

        //找到有序的区间
        while(ub > lb){
            //区间有序，返回
            if(nums[lb] < nums[ub]) return nums[lb];

            int mid = (ub - lb)/2 + lb;

            //左半部分有序的话，那么所求的值一定不在左半边
            if(nums[mid] >= nums[lb])
                lb = mid + 1;
            //右半部分有序的话，可能取到mid
            else
                ub = mid ;
        }
        return nums[lb];
    }
};