Search in Rotated Sorted Array--LeetCode
来源:互联网 发布:天国的水晶宫知轩 编辑:程序博客网 时间:2024/05/24 07:02
1.题目
Search in Rotated Sorted Array
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).
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.
2.题意
将升序数组旋转,找出数组中target的位置,数组中无重复数
3.分析
二分查找,分为以下3种情况:
(1)如果A[m]==target
,直接返回m;
(2)如果A[m]<A[r]
,说明从m到r有序(没有受到rotate的影响)
若target在m到r之间,则把左边界移到m+1
否则就target在另一半,把右边界移到m-1
(3)如果A[m]>=A[r]
,说明从l到m有序
只需要判断target是否在这个范围内,相应的移动边界即可
根据以上方法,每次都可以切掉一半的数据,所以算法的时间复杂度是O(logn),空间复杂度是O(1)
注意mid有可能会等于left
所以如果要把left放前面,那就需要用if(A[l]<=A[m])
4.代码
class Solution {public: int search(vector<int>& nums, int target) { if(nums.size() == 0) return -1; int left = 0; int right = nums.size() - 1; while(left <= right) { int mid = left + (right - left) / 2; if(nums[mid] == target) return mid; if(nums[mid] < nums[right]) { if(nums[mid] < target && target <= nums[right]) left = mid + 1; else right = mid - 1; } else { if(nums[left] <= target && target < nums[mid]) right = mid - 1; else left = mid + 1; } } return -1; }};
阅读全文
0 0
- [leetcode][search] Search in Rotated Sorted Array
- LeetCode: Search in Rotated Sorted Array
- LeetCode: Search in Rotated Sorted Array II
- LeetCode Search in Rotated Sorted Array
- LeetCode Search in Rotated Sorted Array II
- [Leetcode] Search in Rotated Sorted Array
- LeetCode : Search in Rotated Sorted Array
- LeetCode : Search in Rotated Sorted Array II
- [LeetCode] Search in Rotated Sorted Array II
- [LeetCode] Search in Rotated Sorted Array
- [Leetcode] Search in a Rotated Sorted Array
- [Leetcode] Search in Rotated Sorted Array II
- leetcode 97: Search in Rotated Sorted Array
- [LeetCode] Search in Rotated Sorted Array
- [leetcode] Search in Rotated Sorted Array
- [leetcode] Search in Rotated Sorted Array II
- Leetcode Search in Rotated Sorted Array
- [LeetCode]Search in Rotated Sorted Array
- hibernate中的hql语句加select字段与不加的区别
- 2017清华软院推免机考+面经
- 考前冲刺与考点分析-面向对象设计
- Spring系列之AOP
- make/makefile一
- Search in Rotated Sorted Array--LeetCode
- 网络请求与json数据解析——学习笔记
- tic-tac-toe游戏
- JDK学习---深入理解Comparator、TreeSet、TreeMap为什么可以排序
- Struts-servletapi
- Android App开发基础篇—四大组件之Broadcast-01
- SPSS计算Cronbach系数的公式及计算代码
- UVa10564
- HDU