[LeetCode] 154. Find Minimum in Rotated Sorted Array II 寻找旋转有序数组的最小值之二
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?
这道寻找旋转有序重复数组的最小值是之前那道 Find Minimum in Rotated Sorted Array 的拓展,当数组中存在大量的重复数字时,就会破坏二分查找法的机制,将无法取得 O(lgn) 的时间复杂度,又将会回到简单粗暴的 O(n),比如这两种情况:{2, 2, 2, 2, 2, 2, 2, 2, 0, 1, 1, 2} 和 {2, 2, 2, 0, 2, 2, 2, 2, 2, 2, 2, 2},可以发现,当第一个数字和最后一个数字,还有中间那个数字全部相等的时候,二分查找法就崩溃了,因为它无法判断到底该去左半边还是右半边。这种情况下,将右指针左移一位(或者将左指针右移一位),略过一个相同数字,这对结果不会产生影响,因为只是去掉了一个相同的,然后对剩余的部分继续用二分查找法,在最坏的情况下,比如数组所有元素都相同,时间复杂度会升到 O(n),参见代码如下:
解法一:
class Solution {
public:
int findMin(vector<int>& nums) {
int left = , right = (int)nums.size() - ;
while (left < right) {
int mid = left + (right - left) / ;
if (nums[mid] > nums[right]) left = mid + ;
else if (nums[mid] < nums[right]) right = mid;
else --right;
}
return nums[right];
}
};
跟之前那道 Find Minimum in Rotated Sorted Array 一样,还是可以用分治法 Divide and Conquer 来解,还是由热心网友 howard144 提供,不过写法跟之前那道略有不同,只有在 nums[start] < nums[end] 的时候,才能返回 nums[start],等于的时候不能返回,比如 [3, 1, 3] 这个数组,或者当 start 等于 end 成立的时候,也可以直接返回 nums[start],后面的操作跟之前那道题相同,每次将区间 [start, end] 从中间 mid 位置分为两段,分别调用递归函数,并比较返回值,每次取返回值较小的那个即可,参见代码如下:
解法二:
class Solution {
public:
int findMin(vector<int>& nums) {
return helper(nums, , (int)nums.size() - );
}
int helper(vector<int>& nums, int start, int end) {
if (start == end) return nums[start];
if (nums[start] < nums[end]) return nums[start];
int mid = (start + end) / ;
return min(helper(nums, start, mid), helper(nums, mid + , end));
}
};
Github 同步地址:
https://github.com/grandyang/leetcode/issues/154
类似题目:
Find Minimum in Rotated Sorted Array
参考资料:
https://leetcode.com/problems/find-minimum-in-rotated-sorted-array-ii/
LeetCode All in One 题目讲解汇总(持续更新中...)
[LeetCode] 154. Find Minimum in Rotated Sorted Array II 寻找旋转有序数组的最小值之二的更多相关文章
- [LeetCode] 154. Find Minimum in Rotated Sorted Array II 寻找旋转有序数组的最小值 II
Follow up for "Find Minimum in Rotated Sorted Array":What if duplicates are allowed? Would ...
- [LeetCode] Find Minimum in Rotated Sorted Array II 寻找旋转有序数组的最小值之二
Follow up for "Find Minimum in Rotated Sorted Array":What if duplicates are allowed? Would ...
- 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. ( ...
- [LeetCode] Search in Rotated Sorted Array II 在旋转有序数组中搜索之二
Follow up for "Search in Rotated Sorted Array":What if duplicates are allowed? Would this ...
- [LeetCode] 81. Search in Rotated Sorted Array II 在旋转有序数组中搜索之二
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. (i.e. ...
- LeetCode 153. Find Minimum in Rotated Sorted Array (在旋转有序数组中找到最小值)
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. (i.e. ...
- Java for LeetCode 154 Find Minimum in Rotated Sorted Array II
Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 migh ...
- leetcode 154. Find Minimum in Rotated Sorted Array II --------- java
Follow up for "Find Minimum in Rotated Sorted Array":What if duplicates are allowed? Would ...
- [LeetCode#154]Find Minimum in Rotated Sorted Array II
The question: Follow up for "Find Minimum in Rotated Sorted Array":What if duplicates are ...
随机推荐
- Docker Hub镜像加速器
国内从 Docker Hub 拉取镜像有时会遇到困难,此时可以配置镜像加速器.Docker 官方和国内很多云服务商都提供了国内加速器服务. 1.配置加速地址 vim /etc/docker/daemo ...
- Golang Testing单元测试指南
基础 可以通过 go test -h 查看帮助信息. 其基本形式是: go test [build/test flags] [packages] [build/test flags & tes ...
- spring boot入门,看这篇文章就够了
一.SpringBoot入门 1.基本介绍 简化Spring应用开发的一个框架.整个Spring技术栈的一个大整合: J2EE开发的一站式解决方案: 优点: 快速创建独立运行的Spring项目以及与主 ...
- eclipse启动tomcat警告 [SetPropertiesRule]{Server/Service/Engine/Host/Context}
解决问题:解决办法是:关闭tomcat,双击eclipse下tomcat服务器,在出来的Tomcat server at localhost页面中找到server options选项,选中其中的选项” ...
- Eureka自我保护机制源码解析
默认情况下,当EurekaServer在一定时间内(默认90秒)没有接收到某个客户端实例的心跳,EurekaServer将会注销该实例.但是当网络分区故障发生时,客户端与EurekaServer之间无 ...
- VS2010 报错该文件包含不能在当前代码页(936)中表示的字符。请将该文件保存为 Unicode 格式以防止数据丢失
尤其代码是从linux平台复制过来: 报错如图: 更有甚者基本函数都报错: 当下检查发现if else break case等基本函数并无问题时,报错行数明显不一致等一定要注意文档编码格式, 最简单的 ...
- 第九届极客大挑战——怎么又是江师傅的秘密(java反序列化)
这道题其实是考jsp和java的,我没学过jsp,java倒是有一点了解,但是刚拿到题的时候还是看不懂java代码里的内容,所以去简单学习了下jsp(jsp教程),按照教程里的步骤搭建了eclipse ...
- ios视频网盘
http://pan.baidu.com/share/home?uk=1711799154#category/type=0
- foreachRDD
需求: 将统计结果写入到MySQL create table wordcount( word varchar(50) default null, wordcount int(10) default n ...
- 去除数组空格 php
public function trimArray($params){ if (!is_array($params)) return trim($params); return array_map([ ...