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414. Third Maximum Number

Difficulty Topics

Description

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.

 

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

 

Follow up: Can you find an O(n) solution?

Solution

third-maximum-number.py
class Solution:
    def thirdMax(self, nums: List[int]) -> int:
        if not nums: return 0

        first = second = third = float('-inf')

        for num in nums:
            if num > first:
                first, second, third = num, first, second

            elif num > second and num < first:
                second, third = num, second

            elif num > third and num < second:
                third = num

            print(first, second, third)

        return third if third != float('-inf') else first