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128. Longest Consecutive Sequence
Medium
Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.
You must write an algorithm that runs in O(n) time.
Example 1:
Input: nums = [100,4,200,1,3,2]
Output: 4
Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.
Example 2:
Input: nums = [0,3,7,2,5,8,4,6,0,1]
Output: 9
Constraints:
0 <= nums.length <= 105-109 <= nums[i] <= 109
Solution
# @param {Integer[]} nums
# @return {Integer}
def longest_consecutive(nums)
return 0 if nums.empty?
nums.sort!
max = -Float::INFINITY
ths_max = 1
(0..nums.length - 2).each do |i|
if nums[i + 1] == nums[i] + 1
ths_max += 1
next
end
next if nums[i + 1] == nums[i]
# Start of a new sequence
max = [max, ths_max].max
ths_max = 1
end
[max, ths_max].max
end