Implement a Priority Queue

EasyPython

Problem

Nio Robotics uses priority-based scheduling for robot tasks. Implement a priority queue that always returns the task with the smallest priority value, while preserving insertion order when priorities are equal.

Create a function that processes a sequence of operations and returns the results of all query operations.

Formal Specification

Implement priority_queue(operations).

Each operation is one of the following lists:

['push', value, priority]: Insert value with an integer priority. Lower values represent higher priority.
['pop']: Remove and return the highest-priority value. Return None if the queue is empty.
['peek']: Return the highest-priority value without removing it. Return None if the queue is empty.
['is_empty']: Return True if the queue contains no values, otherwise return False.

Return a list containing the result of every pop, peek, and is_empty operation in their original order. The queue must be stable: values with equal priorities are returned in insertion order.

Constraints

1 <= len(operations) <= 10^5
Values are integers or strings
Priorities are integers in [-10^9, 10^9]
At most 10^5 values are present at any time
Equal-priority values must be returned in insertion order

Function Signature

def priority_queue(operations):

Create a function that processes a sequence of operations and returns the results of all query operations.

Formal Specification

Implement priority_queue(operations).

Each operation is one of the following lists:

['push', value, priority]: Insert value with an integer priority. Lower values represent higher priority.
['pop']: Remove and return the highest-priority value. Return None if the queue is empty.
['peek']: Return the highest-priority value without removing it. Return None if the queue is empty.
['is_empty']: Return True if the queue contains no values, otherwise return False.

Return a list containing the result of every pop, peek, and is_empty operation in their original order. The queue must be stable: values with equal priorities are returned in insertion order.