class SortedPriorityQueue(PriorityQueueBase):
"""A min-oriented priority queue implemented with a sorted list."""
def __init__(self):
"""Create a new empty Priority Queue."""
self._data = PositionalList()
def __len__(self):
"""Return the number of items in the priority queue."""
return len(self._data)
def add(self, key, value):
"""Add a key-value pair."""
newest = self._Item(key, value)
walk = self._data.last() # walk backward looking for smaller key
while walk is not None and newest < walk.element():
walk = self._data.before(walk)
if walk is None:
self._data.add_first(newest) # new key is the smallest
else:
self._data.add_after(walk, newest) # newest goes after walk
def min(self):
"""Return but do not remove (k, v) tuple with minimum key."""
if self.is_empty():
raise Empty('Priority queue is empty.')
p = self._data.first()
item = p.element()
return (item._key, item._value)
def remove_min(self):
"""Remove and return (k, v) tuple with minimum key from the priority queue."""
if self.is_empty():
raise Empty('Priority queue is empty.')
item = self._data.delete(self._data.first())
return (item._key, item._value)
def test_delete_validates_and_calls_delete_node_on_position(self):
pl = PositionalList()
expected_element = 'foo'
node = PositionalList._Node(expected_element, None, None)
pl._validate = MagicMock(return_value=node)
pl._delete_node = MagicMock(return_value=expected_element)
position = PositionalList.Position(pl, node)
result_element = pl.delete(position)
pl._validate.assert_called_with(position)
pl._delete_node.assert_called_with(node)
self.assertIs(result_element, expected_element)
class UnsortedPriorityQueue(PriorityQueueBase):
"""A min-oriented priority queue implemented with an unsorted list."""
def _find_min(self):
"""Return Position of item with minimum key."""
if self.is_empty():
raise Empty('Priority queue is empty')
small = self._data.first()
walk = self._data.after(small)
while walk is not None:
if walk.element() < small.element():
small = walk
walk = self._data.after(walk)
return small
def __init__(self):
"""Create a new empty Priority Queue."""
self._data = PositionalList()
def __len__(self):
"""Return the number of items in the priority queue."""
return len(self._data)
def add(self, key, value):
"""Add a key-value pair."""
self._data.add_last(self._Item(key, value))
def min(self):
"""Return but do not remove (k, v) tuple with minimum key."""
p = self._find_min()
item = p.element()
return (item._key, item._value)
def remove_min(self):
"""Remove and return (k, v) tuple with minimum key from the prioriry queue."""
p = self._find_min()
item = self._data.delete(p)
return (item._key, item._value)