Task Scheduler

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Problem

Given an array of CPU tasks (represented by letters) and a cooldown period n — the minimum number of units that must pass between two executions of the same task type — return the minimum number of time units the CPU needs to finish all tasks, allowing idle units when necessary.

Examples

Example 1

Input:tasks = ["A","A","A","B","B","B"], n = 2

Output:8

One valid order: A B idle A B idle A B.

Constraints

1 <= tasks.length <= 10^4
0 <= n <= 100

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How to approach it: the Heap / Priority Queue pattern

A heap keeps the minimum (or maximum) element accessible in O(1), with O(log n) insert and remove. It's the tool whenever you repeatedly need "the smallest/largest remaining item" without needing everything fully sorted.

Look for this pattern when

You need the top-k largest/smallest elements, not a full sort.
You're merging multiple sorted sequences (always take the smallest available head).
You need a running min/max/median as data streams in.

Read the full Heap / Priority Queue guide →

Video walkthroughs

Original problem on LeetCode ↗