【leetcode】33. Search in Rotated Sorted Array
来源:互联网 发布:我想学习编程 编辑:程序博客网 时间:2024/06/06 18:34
Difficulty:hard
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
).
You are given a target value to search. If found in the array return its index, otherwise return -1.
You may assume no duplicate exists in the array.
解题思路(一):顺序遍历时间复杂度O(n)
这种方式使用在解决初级查找问题的,时间复杂度高,但是代码很简单,采用一遍循环比较出最大的数字就可以了、
代码如下:
class Solution {public: int search(vector<int>& nums, int target) { int n=nums.size(); for(int i=0;i<n;i++) { if(nums[i]==target) return i; } return -1; }};解题思路(二):二分查找时间复杂度O(log n)
二分查找要求的是单调的排序序列,但是题目中所给的数列某些部分被倒置。但是这并不影响对二分查找的使用。
首先考虑当arr[m]=target的时候,这时m就是需要的序列。
其次,如果arr[m]<arr[right]时,说明在m于right之间的都是单调的,那么就是正常使用二分搜索,如果arr[m]<target&target>=left left=m+1,如果arr[m]>target right=m-1;
最后,假如arr[m]>arr[right]时,说明在m和right之间有倒置,但是考虑到,如果发生了倒置m右边的最小的数arr[left]是大于arr[right]的,所以,如果arr[m]>target&&target>=arr[left],那么target一定在arr[left]和arr[m]之间了,所以right=m-1,如果target<arr[left]说明target在m到right之间,所以left=m+1;
代码如下:
class Solution {public: int search(vector<int>& nums, int target) { int left=0; int right=nums.size()-1; while(left<=right) { int m=(left+right)/2; if(nums[m]==target) return m; else if(nums[m]<nums[right]) { if(nums[m]<target&&nums[right]>=target) left=m+1; else right=m-1; } else { if(nums[m]>target&&nums[left]<=target) right=m-1; else left=m+1; } } return -1; }};
- [LeetCode]33.Search in Rotated Sorted Array
- LeetCode --- 33. Search in Rotated Sorted Array
- LeetCode 33.Search in Rotated Sorted Array
- [Leetcode] 33. Search in Rotated Sorted Array
- Leetcode-33.Search in Rotated Sorted Array.
- [leetcode] 33. Search in Rotated Sorted Array
- Leetcode 33. Search in Rotated Sorted Array
- [LeetCode]33. Search in Rotated Sorted Array
- leetcode 33. Search in Rotated Sorted Array
- LeetCode *** 33. Search in Rotated Sorted Array
- LeetCode - 33. Search in Rotated Sorted Array
- LeetCode 33. Search in Rotated Sorted Array
- leetcode 33. Search in Rotated Sorted Array
- leetcode 33.Search in Rotated Sorted Array
- [leetcode]33. Search in Rotated Sorted Array
- leetcode 33. Search in Rotated Sorted Array
- leetcode 33. Search in Rotated Sorted Array
- LeetCode-33.Search in Rotated Sorted Array
- qmake生成vcproj & sln
- Linux命令 - cut,grep
- 安装CLion发生错误的解决方法
- 冒泡排序(Bubble Sort)
- 12.Min Stack-带最小值操作的栈(中等题)
- 【leetcode】33. Search in Rotated Sorted Array
- 不是内部或外部命令也不是可运行的程序?
- check the manual that corresponds to your MySQL server version for the right syntax
- Oracle bat批处理文件执行SQL文件
- deeplearning.net 0.1 document - Convolution Neural Networks(LeNet)
- Java中hashCode的作用
- Unity项目图片纹理优化方案
- 初识Linux内核-DIY内核模块
- Spring+Hibernate整合开发配置,完整实例