3254. Find the Power of K-Size Subarrays I

public class Solution
{
    public int[] ResultsArray(int[] nums, int k)
    {
        int n = nums.Length;
        int[] arr = new int[n - k + 1];
        int count = 0;
        for (int i = 1; i < k; i++)
        {
            if (nums[i] == nums[i - 1] + 1)
                count++;
        }

        arr[0] = (count == k - 1) ? nums[k - 1] : -1;
        for (int i = 1; i <= n - k; i++)
        {
            if (nums[i] == nums[i - 1] + 1)
                count--;

            if (nums[i + k - 1] == nums[i + k - 2] + 1)
                count++;

            arr[i] = (count == k - 1) ? nums[i + k - 1] : -1;
        }
        return arr;
    }
}