Third Maximum Number with Java

The challenge

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.

The solution

I have seen many possible resolutions to this problem, but my favourite has to be the following:

class Solution {
    // input a primitive array of ints and return an int
    public int thirdMax(int[] nums) {
        
        // set variables for our 3 max'es
        Integer max1 = null;
        Integer max2 = null;
        Integer max3 = null;
        // loop through the input array
        for (Integer n : nums) {
            // if already set, then skip this loop iteration
            if (n.equals(max1) || n.equals(max2) || n.equals(max3)) continue;
            // if 1
            if (max1 == null || n > max1) {
                max3 = max2;
                max2 = max1;
                max1 = n;
            // if 2
            } else if (max2 == null || n > max2) {
                max3 = max2;
                max2 = n;
            // if 3
            } else if (max3 == null || n > max3) {
                max3 = n;
            }
        }
        // return max3, unless null
        return max3 == null ? max1 : max3;
        
    }
}
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