2461. Maximum Sum of Distinct Subarrays With Length K

Medium

You are given an integer array nums and an integer k. Find the maximum subarray sum of all the subarrays of nums that meet the following conditions:

• The length of the subarray is k, and

• All the elements of the subarray are distinct.

Return the maximum subarray sum of all the subarrays that meet the conditions. If no subarray meets the conditions, return 0.

A subarray is a contiguous non-empty sequence of elements within an array.

Example 1:

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

Example 2:

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.

Constraints:

• 1 <= k <= nums.length <= 105

• 1 <= nums[i] <= 105

解題

func maximumSubarraySum(nums []int, k int) int64 {
    m := make(map[int]int)
    sum := 0
    max := 0

    for i := 0; i < len(nums); i++ {
        sum += nums[i]
        m[nums[i]]++

        if i >= k - 1{
            if len(m) == k && sum > max {
                max = sum
            }

            sum -= nums[i - k + 1]
            m[nums[i - k + 1]]--
            if m[nums[i - k + 1]] == 0 {
                delete(m, nums[i - k + 1])
            }
        }
    }

    return int64(max)
}