[LeetCode][Java] Longest Consecutive Sequence
来源:互联网 发布:淘宝女装店铺排行榜 编辑:程序博客网 时间:2024/05/22 03:28
题目:
Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
For example,
Given [100, 4, 200, 1, 3, 2]
,
The longest consecutive elements sequence is [1, 2, 3, 4]
. Return its length: 4
.
Your algorithm should run in O(n) complexity.
题意:
给定一个未排序的整数数组,返回最长的连续元素的长度。
给定[100, 4, 200, 1, 3, 2]
,
最长连续元素序列为[1, 2, 3, 4].返回它的长度为:4.
你的算法的复杂度应该为O(n) .
算法分析:
* 排序的话至少要O(nlgn) 的复杂度。
* O(n)的复杂度,目前只找到了使用hash来解决的方案,
* add, remove, contains 等方法的复杂度都是 O(1),因此两次遍历的操作复杂度为 O(n)。
* 先把数字放到一个集合中,拿到一个数字,就往其两边搜索,得到包含这个数字的最长串,
* 并且把用过的数字从集合中移除(因为连续的关系,一个数字不会出现在两个串中)。最后比较当前串是不是比当前最大串要长,是则更新。
* 如此继续直到集合为空。
* After an element is checked, it should be removed from the set.
* Otherwise, time complexity would be O(mn) in which m is the average length of all consecutive sequences.
AC代码:
<span style="font-size:12px;">public static int longestConsecutive(int[] num) { // if array is empty, return 0 if (num.length == 0) return 0; Set<Integer> set = new HashSet<Integer>(); int max = 1; for (int e : num) set.add(e); for (int e : num) { int left = e - 1; int right = e + 1; int count = 1; while (set.contains(left)) { count++; set.remove(left); left--; } while (set.contains(right)) { count++; set.remove(right); right++; } max = Math.max(count, max); } return max; }}</span>
- [Leetcode] Longest Consecutive Sequence (Java)
- Longest Consecutive Sequence--Leetcode(Java)
- [leetcode]longest consecutive sequence(java)
- [LeetCode][Java] Longest Consecutive Sequence
- Longest Consecutive Sequence leetcode java
- Leetcode : Longest Consecutive Sequence
- [Leetcode] Longest Consecutive Sequence
- [leetcode] longest consecutive sequence
- 【leetcode】Longest Consecutive Sequence
- LeetCode - Longest Consecutive Sequence
- [LeetCode]Longest Consecutive Sequence
- leetcode:Longest Consecutive Sequence
- [Leetcode]Longest Consecutive Sequence
- [leetcode]Longest Consecutive Sequence
- leetcode Longest Consecutive Sequence
- Leetcode: Longest Consecutive Sequence
- LeetCode:Longest Consecutive Sequence
- [leetcode] Longest Consecutive Sequence
- 【持久化框架】SpringMVC+Spring4+Mybatis3集成,开发简单Web项目
- 编程语言风格概述(中)
- nyoj289-苹果,01背包问题
- 小希的迷宫
- android之布局优化
- [LeetCode][Java] Longest Consecutive Sequence
- CMemDC
- sql——存储过程&触发器(2/3)
- continue和break的使用注意
- php验证码--字符
- youphp的模板使用
- 【IDE-Visual Studio】引用ms32.lib 编译时发现链接错误
- sybase备份恢复
- 单循环链表