Third Maximum Number

Third Maximum Number

Given integer array nums, return the third 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 third maximum is 1.

Example 2:

Input: nums = [1,2]
Output: 2
Explanation: The third maximum does not exist, so the maximum (2) is returned instead.

Example 3:

Input: nums = [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.

Constraints:

• 1 <= nums.length <= 104

• 231 <= nums[i] <= 231 - 1

Follow up: Can you find an O(n) solution?

Solutions

🧠 Cpp

class Solution
{
public:
    int thirdMax(vector<int> nums)
    {
        std::sort(nums.begin(), nums.end());
        nums.erase(std::unique(nums.begin(), nums.end()), nums.end());

        const size_t uniq_size = nums.size();
        if(uniq_size < 3)
            return nums[uniq_size-1];
        else
        {
            return nums[uniq_size-3];
        }
    }
};