Level 5Exercise #107

Stable priority queue

Process tasks by lower numeric priority first, preserving insertion order on ties.

What you’ll practice

This Level 5 exercise focuses on heap tuple in the Algorithms curriculum. Solve the challenge prompt above using clear, idiomatic Python and the relevant language or standard-library tools.

Relevant Python reference: heapq — Heap queue algorithm.

Sample Test Cases

Example #1

Input:task_order([(2,'A'),(1,'B'),(1,'C')])

Output:['B','C','A']

Reference Solution

Reveal Reference Solution

def task_order(tasks: list[tuple[int,str]]) -> list[str]:
    import heapq
    heap = [(priority, i, task) for i, (priority, task) in enumerate(tasks)]
    heapq.heapify(heap)
    return [heapq.heappop(heap)[2] for _ in range(len(heap))]

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Stable priority queue

What you’ll practice

Sample Test Cases

Further Reading

Reference Solution