2017-S3 Nailed It! - Solution

void read_input()
{
    std::cin >> n;
 
    memset(countingSort, 0, sizeof(countingSort));
 
    for (int i = 0; i < n; i++)
    {
        int l;
        std::cin >> l;
        countingSort[l]++;
    }
}

int find_number_of_boards_at_height(int height)
{
    memcpy(lengths, countingSort, sizeof(lengths));
 
    int a = std::max(1, height - 2000);
    int b = height - a;
 
    int num_of_boards = 0;
 
    while (a <= (height / 2))
    {
        if (a == b)
        {
            int boards = lengths[a] / 2;
            lengths[a] -= boards * 2;
 
            num_of_boards += boards;
        }
        else
        {
            int boards = std::min(lengths[a], lengths[b]);
            lengths[a] -= boards;
            lengths[b] -= boards;
 
            num_of_boards += boards;
        }
 
        ++a;
        --b;
    }
 
    return num_of_boards;
}

int main()
{
    read_input();
 
    int max_boards = 0;
    int heights_at_max_boards = 0;
 
    for (int i = 2; i <= 4000; i++)
    {
        int boards = find_number_of_boards_at_height(i);
 
        if (boards > max_boards)
        {
            max_boards = boards;
            heights_at_max_boards = 0;
        }
        if (boards == max_boards)
        {
            heights_at_max_boards++;
        }
    }
 
    std::cout << max_boards << " " << heights_at_max_boards;
    std::cin >> n;
 
    return 0;
}