Longest Consecutive Sequence
Description
Given an unsorted array of integers, find the length of the longest consecutive elements sequence. Well, lets assume that this task related only to the sequence with step equal to 1 only.
For example:
Given exampleArray = [100, 4, 200, 1, 3, 2].
The longest consecutive elements sequence is [1, 2, 3, 4].
longestConsecutiveLength(exampleArray) returns the length of the longest sequence - 4.
Attentive!
Your algorithm should have O(n) complexity.