LeetCode 414. Third Maximum Number

Description

https://leetcode.com/problems/third-maximum-number/

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.

Constraints:

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

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

Explanation

The easiest way is to sort and find the third largest.

Python Solution

class Solution:
    def thirdMax(self, nums: List[int]) -> int:
        
        nums = list(set(nums))
        nums = sorted(nums)
        
        if len(nums) < 3:
            return nums[-1]
        
        return nums[-3]
  • Time Complexity: O(log(N)).
  • Space Complexity: O(N).

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