thirdMax.js

/**
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

* @param {number[]} nums
* @return {number}
*/
var thirdMax = function (nums) {
  let firstMax = (secondMax = thirdMax = Number.MIN_SAFE_INTEGER);

  for (const num of nums) {
    if (num === firstMax || num === secondMax || num === thirdMax) {
      continue;
    }

    if (num > firstMax) {
      thirdMax = secondMax;
      secondMax = firstMax;
      firstMax = num;
    } else if (num > secondMax) {
      thirdMax = secondMax;
      secondMax = num;
    } else if (num > thirdMax) {
      thirdMax = num;
    }
  }

  return thirdMax > Number.MIN_SAFE_INTEGER ? thirdMax : firstMax;
};