Third Maximum Number

Problem Statement

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

Leetcode Link

Examples:

Example 1:

Input: nums = [3,2,1]
Output: 1
Explanation:
The first distinct maximum is 3.
The second distinct maximum is 2.
The third distinct maximum is 1.


Example 2:

Input: nums = [1,2]
Output: 2
Explanation:
The first distinct maximum is 2.
The second distinct maximum is 1.
The third distinct maximum does not exist, so the maximum (2) is returned instead.


Example 3:

Input: nums = [2,2,3,1]
Output: 1
Explanation:
The first distinct maximum is 3.
The second distinct maximum is 2 (both 2's are counted together since they have the same value).
The third distinct maximum is 1.

Constraints:

• 1 <= nums.length <= 10⁴
• -2³¹ <= nums[i] <= 2³¹ - 1

Code

Python Code

class Solution:
    def thirdMax(self, nums: List[int]) -> int:
        if len(nums) >= 3:
            checked = set()
            count = 0
            nums.sort()
            for i in range(len(nums) - 1, -1, -1):
                if nums[i] not in checked:
                    if count == 2:
                        return nums[i]
                    else:
                        checked.add(nums[i])
                        count += 1
            return max(nums)
        else:
            return max(nums)