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.
Examples
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
Example 3
Input: nums = [1,0,1,2]
Output: 3
Constraints
0 <= nums.length <= 105
-109 <= nums[i] <= 109
128. Longest Consecutive Sequence
Medium
30 Points
Array
Hash Table
Union Find
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.
Examples
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
Example 3
Input: nums = [1,0,1,2]
Output: 3
Constraints
0 <= nums.length <= 105
-109 <= nums[i] <= 109
Longest Consecutive Sequence - Practice Coding | SlaveCode