public class Solution
extends Object
414 - Third Maximum Number\.
Easy
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?