class Solution {
public:
    int findMin(vector<int>& nums) {
        //处理数组为空的情况
        if(nums.empty())    return -1;
        int l = -1;
        int r = nums.size() - 1;
        while(l + 1 != r){
            int mid = (l + r) >> 1;
            //核心步骤
            if(nums[mid] < nums[r]){
                r = mid;
            }else{
                l = mid;
            }
        }
        return nums[r];
    }
};