Sliding window-> Max sum of distinct subarray

import java.util.*;

class Main {
    public static int maxSumDistinctSubarray(int[] nums, int k) {
        int n = nums.length;
        int left = 0;
        int currentSum = 0;
        int maxSum = 0;
        
        HashMap<Integer, Integer> freq = new HashMap<>(); // track counts of elements
        
        for (int right = 0; right < n; right++) {
            int num = nums[right];
            freq.put(num, freq.getOrDefault(num, 0) + 1);
            currentSum += num;
            
            // shrink window if size exceeds k or duplicates exist
            while (freq.get(num) > 1 || (right - left + 1) > k) {
                int leftNum = nums[left];
                freq.put(leftNum, freq.get(leftNum) - 1);
                currentSum -= leftNum;
                left++;
            }
            
            // if valid window of size k with distinct elements
            if (right - left + 1 == k) {
                maxSum = Math.max(maxSum, currentSum);
            }
        }
        
        return maxSum;
    }

    public static void main(String[] args) {
        int nums[] = {1, 5, 4, 2, 9, 9, 9};
        int k = 3;
        System.out.println(maxSumDistinctSubarray(nums, k)); // should print 15 (from [5,4,6] or [4,2,9])
    }
}