128. Longest Consecutive Sequence

class Solution {
    public int longestConsecutive(int[] nums) {
        if (nums.length < 1) {
            return 0; 
        }
        
        Arrays.sort(nums);
        
        int longest = 1;
        int curLong = 1;
    
        int prev = nums[0];
        for (int i = 1; i < nums.length; i++) {
            if (nums[i] == prev + 1) {
                curLong++;
            } else if (nums[i] > prev + 1 || nums[i] < prev) {
                curLong = 1;
            }
            prev = nums[i];
            
            if (curLong >= longest) {
                longest = curLong; 
            }
        }
        
        return longest; 
    }
}

Runtime: 2 ms, faster than 99.51% of Java online submissions for Longest Consecutive Sequence.
Memory Usage: 39.1 MB, less than 73.81% of Java online submissions for Longest Consecutive Sequence.

내사랑 sort...^^

class Solution {
    public int longestConsecutive(int[] nums) {
        Set<Integer> num_set = new HashSet<Integer>();
        for (int num : nums) {
            num_set.add(num);
        }

        int longestStreak = 0;

        for (int num : num_set) {
            if (!num_set.contains(num-1)) {
                int currentNum = num;
                int currentStreak = 1;

                while (num_set.contains(currentNum+1)) {
                    currentNum += 1;
                    currentStreak += 1;
                }

                longestStreak = Math.max(longestStreak, currentStreak);
            }
        }

        return longestStreak;
    }
}

Runtime: 3 ms, faster than 86.59% of Java online submissions for Longest Consecutive Sequence.
Memory Usage: 39.3 MB, less than 63.48% of Java online submissions for Longest Consecutive Sequence.

루션이
내사랑 쉬셋이 사용