:orphan:

Task Scheduler
==============

.. highlight:: none

Problem
-------
https://leetcode.com/problems/task-scheduler/

You are given an array of CPU tasks, each represented by letters ``A``
to ``Z``, and a cooling time, ``n``. Each cycle or interval allows the
completion of one task. Tasks can be completed in any order, but
there's a constraint: **identical tasks must be separated by at least**
``n`` **intervals** due to cooling time.

Return the *minimum number of intervals* the CPU will take to finish
all the given tasks.



**Example 1:**

::

   Input: tasks = ["A","A","A","B","B","B"], n = 2
   Output: 8
   Explanation: A possible sequence is: A -> B -> idle -> A -> B -> idle -> A -> B.

**Example 2:**

::

   Input: tasks = ["A","C","A","B","D","B"], n = 1
   Output: 6
   Explanation: A possible sequence is: A -> B -> C -> D -> A -> B.

**Example 3:**

::

   Input: tasks = ["A","A","A","B","B","B"], n = 3
   Output: 10
   Explanation: A possible sequence is: A -> B -> idle -> idle -> A -> B -> idle -> idle -> A -> B.



**Constraints:**

- ``1 <= tasks.length <= 10``\ :sup:`4`
- ``tasks[i]`` is an uppercase English letter.
- ``0 <= n <= 100``

.. highlight:: python

Pattern
-------
Heap, Greedy, Hash Table

Approaches
----------

.. tab-set::

    .. tab-item:: Greedy

        **Code**

        .. literalinclude:: ../problems/medium/task-scheduler/task_scheduler__greedy.py
            :language: python
            :lines: 11-

        **Test**

        >>> from task_scheduler__greedy import leastInterval
        >>> leastInterval(["A","A","A","B","B","B"], 2)
        8
        >>> leastInterval(["A","C","A","B","D","B"], 1)
        6
        >>> leastInterval(["A","A","A","B","B","B"], 3)
        10

        .. autofunction:: task_scheduler__greedy.leastInterval

    .. tab-item:: Max Heap

        **Code**

        .. literalinclude:: ../problems/medium/task-scheduler/task_scheduler__max_heap.py
            :language: python
            :lines: 11-

        **Test**

        >>> from task_scheduler__max_heap import leastInterval
        >>> leastInterval(["A","A","A","B","B","B"], 2)
        8
        >>> leastInterval(["A","C","A","B","D","B"], 1)
        6
        >>> leastInterval(["A","A","A","B","B","B"], 3)
        10

        .. autofunction:: task_scheduler__max_heap.leastInterval