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LeetCode 3408: Design Task Manager Solution

Master LeetCode problem 3408 (Design Task Manager), a medium 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.

Problem Explanation

Explanation

To solve this problem, we can use a priority queue to efficiently retrieve and execute tasks with the highest priority. We can also maintain a mapping of taskId to its respective userId for quick retrieval during task execution.

  1. Initialize the TaskManager class with a vector of user-task-priority triples.
  2. Implement the add method to add a new task for a given user.
  3. Implement the edit method to update the priority of an existing task.
  4. Implement the rmv method to remove a task from the system.
  5. Implement the execTop method to execute the task with the highest priority and return the userId associated with that task.

Time Complexity

  • Initialization: O(nlogn) where n is the number of tasks initially provided.
  • add: O(logn) to add a task.
  • edit: O(n) to find and update the priority of the task.
  • rmv: O(n) to remove the task.
  • execTop: O(logn) to execute the top task.

Space Complexity

  • O(n) where n is the number of tasks initially provided.

Solution Code

import java.util.*;

class TaskManager {
    private Map<Integer, Integer> taskIdToUserId;
    private PriorityQueue<int[]> tasksQueue;

    public TaskManager(int[][] tasks) {
        taskIdToUserId = new HashMap<>();
        tasksQueue = new PriorityQueue<>((a, b) -> a[2] != b[2] ? b[2] - a[2] : b[1] - a[1]);

        for (int[] task : tasks) {
            tasksQueue.offer(task);
            taskIdToUserId.put(task[1], task[0]);
        }
    }

    public void add(int userId, int taskId, int priority) {
        int[] newTask = new int[]{userId, taskId, priority};
        tasksQueue.offer(newTask);
        taskIdToUserId.put(taskId, userId);
    }

    public void edit(int taskId, int newPriority) {
        int userId = taskIdToUserId.get(taskId);
        tasksQueue.removeIf(task -> task[1] == taskId);
        tasksQueue.offer(new int[]{userId, taskId, newPriority});
    }

    public void rmv(int taskId) {
        tasksQueue.removeIf(task -> task[1] == taskId);
    }

    public int execTop() {
        if (tasksQueue.isEmpty()) {
            return -1;
        }
        int[] task = tasksQueue.poll();
        taskIdToUserId.remove(task[1]);
        return task[0];
    }
}

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