55 lines
1.5 KiB
Python
55 lines
1.5 KiB
Python
import heapq
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from sys import maxsize
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from typing import Generic, List, Tuple, TypeVar
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_T1 = TypeVar("_T1")
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class PriorityQueue(Generic[_T1]):
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"""Priority queue for scheduling. Note that methods aren't thread-safe."""
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MIN_COUNT = ~maxsize
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def __init__(self) -> None:
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self.items: List[Tuple[_T1, int]] = []
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self.count = PriorityQueue.MIN_COUNT # Monotonic increasing for sort stability
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def __len__(self) -> int:
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"""Returns length of queue"""
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return len(self.items)
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def peek(self) -> _T1:
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"""Returns first item in queue without removing it"""
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return self.items[0][0]
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def dequeue(self) -> _T1:
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"""Returns and removes item with lowest priority from queue"""
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item: _T1 = heapq.heappop(self.items)[0]
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if not self.items:
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self.count = PriorityQueue.MIN_COUNT
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return item
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def enqueue(self, item: _T1) -> None:
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"""Adds item to queue"""
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heapq.heappush(self.items, (item, self.count))
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self.count += 1
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def remove(self, item: _T1) -> bool:
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"""Remove given item from queue"""
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for index, _item in enumerate(self.items):
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if _item[0] == item:
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self.items.pop(index)
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heapq.heapify(self.items)
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return True
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return False
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def clear(self) -> None:
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"""Remove all items from the queue."""
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self.items = []
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self.count = PriorityQueue.MIN_COUNT
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