414. Third Maximum Number
https://leetcode.com/problems/third-maximum-number/
Time - O(n log 3) => O(n)
Space - O(n) - for Set, PQ also has contains method that can reduce space to O(1)
Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must be in O(n).
Example 1:
Input: [3, 2, 1] Output: 1 Explanation: The third maximum is 1.
Example 2:
Input: [1, 2] Output: 2 Explanation: The third maximum does not exist, so the maximum (2) is returned instead.
Example 3:
Input: [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.---
Time - O(n log 3) => O(n)
Space - O(n) - for Set, PQ also has contains method that can reduce space to O(1)
