96. Longest Consecutive Sequence

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Example 1:

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

Output: 4

Explanation: The longest consecutive sequence is [1, 2, 3, 4], which has a length of 4.

Example 2:

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

Output: 9

Explanation: The longest consecutive sequence is [0, 1, 2, 3, 4, 5, 6, 7, 8], which has a length of 9.

Example 3:

Input: nums = [1,0,1,2]

Output: 3

Explanation: The longest consecutive sequence is [0, 1, 2], which has a length of 3. Duplicates are handled.

Example 4:

Input: nums = []

Output: 0

Explanation: An empty array has no consecutive sequence, so the length is 0.

Example 5:

Input: nums = [5]

Output: 1

Explanation: An array with a single element has a consecutive sequence of length 1.

Constraints:

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Time Complexity

O(n)

Space Complexity