Longest Consecutive Subsequence

In this class, We discuss the Longest Consecutive Subsequence.

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Question:

Given an array of positive integers.

Find the length of the longest sub-sequence such that the elements in the sequence are consecutive.

Example:

Input: A = [9, 8, 1, 2, 7, 3, 4]

Output: 4

The above elements have sub-sequence 7, 8, 9, and 1,2, 3, 4

The sub-sequence 1, 2, 3, and 4 has the longest length of 4.

The output is 4.

Time complexity: O(N)

Space complexity: O(N)

Logic:

We use a hash table to write a program in the time O(N).

The step-by-step explanation is provided in the video.

Code: