[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.

Solution:

Sort words to at least O (nlgn) complexity. O (n) complexity, currently only found using hash to solve the scheme, add, remove, contains and other methods of the complexity is O (1), so two times the operation of the traversal is O (n).

 Public classSolution { Public intLongestconsecutive (int[] num) {        if(num==NULL|| Num.length==0)            return0; HashSet<Integer> hs=NewHashset<integer>();  for(inti:num)        {Hs.add (i); }        intMax=1;  for(inte:num) {            intLeft=e-1; intRight=e+1; intTemp=1;  while(Hs.contains (left)) {Hs.remove (left); In fact, it is equivalent to the NUM array to group, each element has been left only once temp++; Left--; }             while(Hs.contains (right)) {Hs.remove (right); Ditto Right++; Temp++; } Max=Math.max (max, temp); }        returnMax; }}

[Leetcode] longest consecutive Sequence