3201. Find the Maximum Length of Valid Subsequence I

public class Solution
{
    public int MaximumLength(int[] nums)
    {
        int k = 2; // Define the modulus value
        int[,] frequency = new int[k, k]; // Initialize a 2D array to hold frequency counts
        int maxLength = 0; // Variable to store the maximum length found

        for (int i = 0; i < nums.Length; i++) // Iterate over the elements in nums array
        {
            int num = nums[i];
            num %= k; // Calculate modulo of num with k
            for (int j = 0; j < k; ++j)
            { // Iterate over each possible value modulo k
                int y = (j - num + k) % k; // Calculate the required complement to make a sum divisible by k
                frequency[num, y] = frequency[y, num] + 1; // Update the frequency table with current element
                maxLength = Math.Max(maxLength, frequency[num, y]); // Update the maximum length found
            }
        }

        return maxLength; // Return the maximum length of subarray found
    }
}