Problem Longest Consecutive Sequence

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     }

Problem Longest Consecutive Sequence