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 

should be [1, 2, 3, 4]. Its length is 4.

Your algorithm should run in O(n) complexity.

将数组放入map中，向左右减一加一查找，查找过的数字直接跳过。

public int longestConsecutive(int[] nums) {
	HashMap<Integer, Integer> hs = new HashMap<Integer, Integer>();
	for(int i: nums)
		hs.put(i, 0);
	int maxl = 1;
	for(int i: nums){
		if (hs.get(i) == 1) continue;
		int tmp = i;
		int current_max = 1;
		while(hs.containsKey(tmp+1)){
			current_max ++;
			tmp ++;
			hs.put(tmp, 1);
		}
		tmp = i;
		while(hs.containsKey(tmp-1)){
			current_max ++;
			tmp --;
			hs.put(tmp, 1);
		}
		maxl = Math.max(current_max, maxl);
	}
	return maxl;
}