Maximum Sum of Distinct Subarrays With Length

lcpy gen -n 2461   # by problem number
lcpy gen -s maximum_sum_of_distinct_subarrays_with_length_k   # by problem name

Input: nums = [1,5,4,2,9,9,9], k = 3
Output: 15
Explanation: The subarrays of nums with length 3 are:
- [1,5,4] which meets the requirements and has a sum of 10.
- [5,4,2] which meets the requirements and has a sum of 11.
- [4,2,9] which meets the requirements and has a sum of 15.
- [2,9,9] which does not meet the requirements because the element 9 is repeated.
- [9,9,9] which does not meet the requirements because the element 9 is repeated.
We return 15 because it is the maximum subarray sum of all the subarrays that meet the conditions

Input: nums = [4,4,4], k = 3
Output: 0
Explanation: The subarrays of nums with length 3 are:
- [4,4,4] which does not meet the requirements because the element 4 is repeated.
We return 0 because no subarrays meet the conditions.

class Solution:
    # Time: O(n)
    # Space: O(k)
    def maximum_subarray_sum(self, nums: list[int], k: int) -> int:
        counts: dict[int, int] = {}
        window_sum = 0
        best = 0

        for i, val in enumerate(nums):
            counts[val] = counts.get(val, 0) + 1
            window_sum += val

            if i >= k:
                left = nums[i - k]
                window_sum -= left
                counts[left] -= 1
                if counts[left] == 0:
                    del counts[left]

            if i >= k - 1 and len(counts) == k:
                best = max(best, window_sum)

        return best