LeetCode： Third Maximum Number

Question

Given integer array nums, return the third maximum number in this array. If the third maximum does not exist, return the maximum number.

Example 1:

Input: nums = [3,2,1]

Output: 1

Explanation: The third maximum is 1.

Example 2:

Input: nums = [1,2]

Output: 2

Explanation: The third maximum does not exist, so the maximum (2) is returned instead.

Example 3:

Input: nums = [2,2,3,1]

Output: 1

Explanation: Note that the third maximum here means the third maximum distinct number. Both numbers with value 2 are both considered as second maximum.

Solution

def third_max(nums)
  third_max_number = nums.uniq.sort[-3]
  third_max_number.nil? ? nums.max : third_max_number
end