Problem

Given an unsorted integer array nums, determine the length of the longest sequence of consecutive elements.

Can you do it in O(n) time?

Examples

longestSequence([10, 5, 12, 3, 55, 30, 4, 11, 2, 6])
// return 5
// Why? Longest sequence is [2, 3, 4, 5, 6]

longestSequence([1, 3, 5, 7, 2, 11])
// return 3
// Why? Longest sequence is [1, 2, 3]