Third Maximum Number

Description

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.

Code

Java

public int thirdMax(int[] nums) {
    final long minNum = Long.MIN_VALUE;
    long firstMax = minNum;
    long secondMax = minNum;
    long thirdMax = minNum;
    for (int num : nums) {
        firstMax = Math.max(firstMax, num);
    }
    for (int num : nums) {
        if (num != firstMax) {
            secondMax = Math.max(secondMax, num);
        }
    }
    for (int num : nums) {
        if (num != firstMax && num != secondMax) {
            thirdMax = Math.max(thirdMax, num);
        }
    }
    return (int) (thirdMax == minNum ? firstMax : thirdMax);
}

Java