Task Scheduler - Medium Python Heap / Priority Queue Interview Problem

You are given an array of CPU tasks, each labeled with a letter from A to Z. The CPU can execute one task per interval. For each interval, the CPU can either:

Complete one of the tasks, or
Sit idle.

However, there is a cooldown interval n between two tasks with the same label. That is, there must be at least n intervals between any two executions of the same task label.

Return the minimum number of intervals required to complete all tasks.

Example 1

Input: tasks = ["A","A","A","B","B","B"], n = 2
Output: 8
Explanation: A -> B -> idle -> A -> B -> idle -> A -> B
             Each A must wait 2 intervals before the next A.

Example 2

Input: tasks = ["A","A","A","A","A","A","B","C","D","E","F","G"], n = 2
Output: 16
Explanation: A -> B -> C -> A -> D -> E -> A -> F -> G -> A -> idle -> idle -> A -> idle -> idle -> A
             Task A runs 6 times and dominates the schedule.

Constraints

1 <= tasks.length <= 10^4
tasks[i] is an uppercase English letter.
0 <= n <= 100

Hints