标签：lex nta and longest should input div contain val
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.
Solution1: Sort it.
Solution2: Use hashmap to store consecutive intervals information, make sure the lowest and the highest both point to length of consecutive interval, such as [0,1,2,3,4], then (0->5, 4->5).
class Solution { public int longestConsecutive(int[] nums) { HashMap<Integer,Integer> map = new HashMap<Integer,Integer>(); int max = 0; for (int n : nums) { if (map.containsKey(n)) continue; map.put(n,1); int a = map.getOrDefault(n-1,0), b = map.getOrDefault(n+1,0); int newval = a+b+1; max = Math.max(max,newval); if (a == 0 && b == 0) continue; //no neighbor map.put(n-a,newval); //update lowest map.put(n+b,newval); //update highest } return max; } }
Longest Consecutive Sequence--记录区间信息
标签：lex nta and longest should input div contain val
原文地址：https://www.cnblogs.com/liudebo/p/9320727.html
