2461. Maximum Sum of Distinct Subarrays With Length K

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.

class Solution {
public:
    long long maximumSubarraySum(vector<int>& A, int k) {
        long long res = 0, now = 0;
        unordered_map<int, int> freq;
        for(int i = 0; i < A.size(); i++) {
            freq[A[i]] += 1;
            now += A[i];
            if(i >= k) {
                if(--freq[A[i-k]] == 0) freq.erase(A[i-k]);
                now -= A[i-k];
            }
            if(freq.size() == k) res = max(res, now);
        }
        return res;
    }
};