LeetCode 2756: Query Batching Solution

Master LeetCode problem 2756 (Query Batching), a hard challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2756. Query Batching

Hard

Problem Explanation

Explanation

To solve this problem, we can use a priority queue to store the queries based on their deadlines. We will iterate over each query and process it based on its deadline while keeping track of the current time. If the current time is less than the query's deadline, we process the query immediately. If not, we batch the query with other pending queries and process them together when the current time reaches the query's deadline.

Algorithm:

Create a priority queue to store the queries based on their deadlines.
Iterate over each query in the input list.
Check if the current time is less than the query's deadline.
If yes, process the query immediately.
If no, batch the query with other pending queries and process them together when the current time reaches the query's deadline.
Update the current time accordingly.

Time Complexity: O(n log n) where n is the number of queries. Space Complexity: O(n) for the priority queue.

Solution Code

import java.util.*;

class Query {
    int id;
    int deadline;

    public Query(int id, int deadline) {
        this.id = id;
        this.deadline = deadline;
    }
}

public List<List<Integer>> queryBatching(List<List<Integer>> queries) {
    PriorityQueue<Query> pq = new PriorityQueue<>((a, b) -> a.deadline - b.deadline);
    List<List<Integer>> result = new ArrayList<>();
    int currentTime = 0;

    for (int i = 0; i < queries.size(); i++) {
        List<Integer> query = queries.get(i);
        int id = query.get(0);
        int deadline = query.get(1);

        if (currentTime < deadline) {
            List<Integer> batchedQuery = new ArrayList<>();
            batchedQuery.add(id);
            batchedQuery.add(deadline);
            result.add(batchedQuery);
        } else {
            List<Integer> lastBatchedQuery = result.get(result.size() - 1);
            lastBatchedQuery.add(id);
        }

        pq.offer(new Query(id, deadline));

        while (!pq.isEmpty() && pq.peek().deadline <= currentTime) {
            Query q = pq.poll();
            List<Integer> batchedQuery = new ArrayList<>();
            batchedQuery.add(q.id);
            batchedQuery.add(q.deadline);
            result.add(batchedQuery);
        }

        currentTime++;
    }

    return result;
}

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