LeetCode 刷题【128. 最长连续序列】

128. 最长连续序列

自己做

解1：排序

class Solution {
    public int longestConsecutive(int[] nums) {
        if(nums.length == 0)
            return 0;

        //排序
        Arrays.sort(nums);

        int max = 1;
        int len = 1;

        for(int i = 1; i < nums.length; i++){
            if(i > 1 && nums[i] == nums[i - 1])
                nums[i - 1] = nums[i - 2];
            else if(nums[i] == nums[i - 1] + 1)
                len++;
            else
                len = 1;

            if(len > max)
                max = len;
        }

        return max;
    }
}

看题解

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;
    }
}