标签：NPU longest tput math class lex int ted complex
Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
Your algorithm should run in O(n) complexity.
Example:
Input: [100, 4, 200, 1, 3, 2]
Output: 4
Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.
class Solution { public int longestConsecutive(int[] nums) { HashSet<Integer> set = new HashSet<Integer>(); for(int i : nums) set.add(i); int res = 0; for(int i: nums){ int len = 1; for(int j = i-1; set.contains(j); j--){ len++; set.remove(j); } for(int k = i+1; set.contains(k); k++){ len++; set.remove(k); } res = Math.max(len, res); } return res; } }
划重点！HashSet的查找的效率是O(1),所以加上遍历才能达到O（n）
思想是以该元素为中心，往左右扩张，直到不连续为止，记录下最长的长度。
128. Longest Consecutive Sequence
标签：NPU longest tput math class lex int ted complex
原文地址：https://www.cnblogs.com/wentiliangkaihua/p/10509826.html
