Longest Consecutive Sequence (medium)
Problem Statement
Given an unsorted array of integers, find the length of the longest consecutive sequence of numbers in it. A consecutive sequence means the numbers in the sequence are contiguous without any gaps. For instance, 1, 2, 3, 4 is a consecutive sequence, but 1, 3, 4, 5 is not.
Examples

 Input: [10, 11, 14, 12, 13]
 Output: 5
 Justification: The entire array forms a consecutive sequence from 10 to 14.

 Input: [3, 6, 4, 100, 101, 102]
 Output: 3
 Justification: There are two consecutive sequences, [3, 4] and [100,101,102]. The latter has a maximum length of 3.

 Input: [4, 3, 6, 2, 5, 8, 4, 7, 0, 1]
 Output: 9
 Justification: The longest consecutive sequences here are [0, 1, 2,, 3, 4, 5, 6, 7, 8].

 Input: [7, 8, 10, 11, 15]
 Output: 2
 Justification: The longest consecutive sequences here are [7,8] and [10,11], both of length 2.
Try it yourself
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Python3
Python3
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