LeetCode 154. Find Minimum in Rotated Sorted Array II寻找旋转排序数组中的最小值 II (C++)

题目:

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.

The array may contain duplicates.

Example 1:

Input: [1,3,5]
Output: 1

Example 2:

Input: [2,2,2,0,1]
Output: 0

Note:

  • This is a follow up problem to Find Minimum in Rotated Sorted Array.
  • Would allow duplicates affect the run-time complexity? How and why?

分析:

这道题是153题的延申,153题链接在这里https://www.cnblogs.com/silentteller/p/11163491.html

多了一个限制,也就是允许重复元素出现,所以一次划分后就不会像153题那样出现一个有序数组和一个有可能有序数组的结果。

比如[3,3,3,3,1,3]划分后[3,3,3]和[3,1,3]两个数组均无序,所以要继续对这两个数组进行划分,而且当左右两端元素相同时,不能单纯的认为其内元素都相同,要继续划分,直到出现左端元素小于右端元素为止。

程序和153题相同,因为在判断数组是否有序的时候时严格判断左端值小于右端值的。

程序:

class Solution {
public:
    int findMin(vector<int>& nums) {
        if(nums.size()==1) return nums[0];
        int l = 0;
        int r = nums.size()-1;
        return find(nums, l, r);
    }
    int find(vector<int>& nums, int l, int r){
        if(nums[l] < nums[r] || l==r) return nums[l];
        if(r-l == 1) return min(nums[l], nums[r]);
        int mid = (l+r)/2;
        return min(find(nums, l, mid-1), find(nums, mid, r));
    }
};
posted @ 2019-07-10 16:37  silentteller  阅读(...)  评论(... 编辑 收藏