Problem Description:
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.
Solution:
1 public int longestConsecutive(int[] num) { 2 Set<Integer> set = new HashSet<Integer>(); 3 4 for (int e : num) { 5 set.add(e); 6 } 7 int max = 1; 8 for (int e : num) { 9 int left = e -1; 10 int right = e + 1; 11 int count = 1; 12 13 while (set.contains(left)) { 14 count++; 15 set.remove(left); 16 left--; 17 } 18 19 while (set.contains(right)) { 20 count++; 21 set.remove(right); 22 right++; 23 } 24 25 max = Math.max(max, count); 26 } 27 28 return max; 29 }
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Problem Longest Consecutive Sequence
原文：http://www.cnblogs.com/liew/p/3815103.html