621. Task Scheduler

Given CPU tasks labeled with letters and a cooldown n, identical tasks must be at least n intervals apart. Each interval runs one task or idles. Return the minimum number of intervals to finish every task.

The most frequent task (count f) forces f − 1 frames of length n + 1, plus a final partial frame holding every task tied for the max. If there are enough other tasks to fill all gaps, the answer is just the number of tasks.

1function leastInterval(tasks: string[], n: number): number {
2  const count = new Map<string, number>();
3  for (const x of tasks) count.set(x, (count.get(x) ?? 0) + 1);
4  const f = Math.max(...count.values());
5  const tied = [...count.values()].filter((c) => c === f).length;
6  return Math.max(tasks.length, (f - 1) * (n + 1) + tied);
7}