readme.md

128. Longest Consecutive Sequence

Medium

Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.

You must write an algorithm that runs in O(n) time.

Example 1:

Input: nums = [100,4,200,1,3,2]

Output: 4

Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.

Example 2:

Input: nums = [0,3,7,2,5,8,4,6,0,1]

Output: 9

Constraints:

• 0 <= nums.length <= 105
• -109 <= nums[i] <= 109

Solution

public class Solution {
    public int LongestConsecutive(int[] nums) {
        if (nums.Length == 0) {
            return 0;
        }
        Array.Sort(nums);
        int max = int.MinValue;
        int thsMax = 1;
        for (int i = 0; i < nums.Length - 1; i++) {
            if (nums[i + 1] == nums[i] + 1) {
                thsMax += 1;
                continue;
            }
            if (nums[i + 1] == nums[i]) {
                continue;
            }
            // Start of a new Sequene
            max = Math.Max(max, thsMax);
            thsMax = 1;
        }
        return Math.Max(max, thsMax);
    }
}