class Solution {
    public int longestConsecutive(int[] nums) {
        if(nums.length <= 1)return nums.length;
        //set可以去重
        Set<Integer> set = new HashSet<Integer>();
        for(int num:nums){
            set.add(num);
        }
        int longest = 0; int currentLongest = 1;
        for(int num:nums){
            currentLongest = 1;
            if(!set.contains(num-1)){
                while(set.contains(num+1)){
                    currentLongest++;
                    num++;
                }
                if(currentLongest > longest)longest = currentLongest;
            }
        }
        return longest;
    }
}