LeetCode Longest Consecutive Sequence

 1 public class Solution {
 2     public int longestConsecutive(int[] nums) {
 3         if(nums == null || nums.length == 0){
 4             return 0;
 5         }
 6         HashSet<Integer> hs = new HashSet<Integer>();
 7         //put every element into hashset
 8         for(int i = 0; i<nums.length; i++){
 9             hs.add(nums[i]);
10         }
11         int res = 0;
12         for(int i = 0; i<nums.length; i++){
13             if(hs.contains(nums[i])){
14                 int count = 1;
15                 //check how many nodes are there in lower branch
16                 int low = nums[i] - 1;
17                 while(hs.contains(low)){
18                     hs.remove(low);
19                     low--;
20                     count++;
21                 }
22                 //check how many nodes are there in higher branch
23                 int high = nums[i] + 1;
24                 while(hs.contains(high)){
25                     hs.remove(high);
26                     high++;
27                     count++;
28                 }
29                 res = Math.max(res,count);
30             }
31         }
32         return res;
33     }
34 }