leetcode -- Longest Consecutive Sequence

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.

large data TLE

public class Solution {
    public int longestConsecutive(int[] num) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int result = 0;
        HashSet<Integer> con = new HashSet<Integer>();
        for(int i = 0; i < num.length; i++){
            int tmpLen = 1;
            int val = num[i];
            con.add(val);
            while(con.contains(--val)){
                tmpLen ++;
            }
            val = num[i];
            while(con.contains(++val)){
                tmpLen ++;
            }
            
            if(tmpLen > result){
                result = tmpLen;
            }
        }
        
        return result;
    }
}

 refactor：

1.使用HashSet来去重

2.遍历数组，循环查看每个元素的相邻元素：

i.检查num-1是否在Set中(loop)，如在则从Set中去除

i.检查num+1是否在Set中(loop)，如在则从Set中去除

public int longestConsecutive(int[] num) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int result = 0;
        HashSet<Integer> con = new HashSet<Integer>();
        for(int i = 0; i < num.length; i++){
            con.add(num[i]);
        }
        
        for(int i = 0; i < num.length; i++){
            int tmpLen = 1;
            int val = num[i];
            while(con.contains(--val)){
                con.remove(val);                
                tmpLen ++;
            }
            val = num[i];
            while(con.contains(++val)){
                con.remove(val);
                tmpLen ++;
            }
            con.remove(num[i]);
            
            if(tmpLen > result){
                result = tmpLen;
            }
        }
        
        return result;
    }