def build_huffman_tree(frequency_table: dict[str, int]) -> Node:
priority_queue = Priority_Queue()
for symbol in frequency_table:
priority_queue.insert(Node(priority=frequency_table[symbol], symbol=symbol))
while len(priority_queue) > 1:
left_child = priority_queue.pull()
right_child = priority_queue.pull()
combined_priority = left_child.priority + right_child.priority
priority_queue.insert(Node(priority=combined_priority, left_child=left_child, right_child=right_child))
return priority_queue.pull()
def test_peek(m_eq, m_lbh, m_hbl):
assert isinstance(m_eq.peek(), type(None))
assert m_lbh.peek() == -1
assert m_hbl.peek() == -1
# Only low priority items in the list.
q = Priority_Queue(2)
q.insert('eh', 1)
assert q.peek() == 'eh'
q.insert('again', 1)
assert q.peek() == 'eh'
def m_hbl(request):
q = Priority_Queue(2)
for x in range(-1, -6, -1):
q.insert(x, 0)
for x in range(5):
q.insert(x, 1)
return q
def test_pop(m_eq, m_lbh, m_hbl):
# pop() an empty Priority_Queue.
with pytest.raises(IndexError):
m_eq.pop()
# Low before high priority and high before low enqueued should not
# affect the order of these when popped off
for x in range(-1, -6, -1):
assert m_lbh.pop() == x
assert m_hbl.pop() == x
for x in range(5):
assert m_lbh.pop() == x
assert m_hbl.pop() == x
# Only high priority items in the list.
q = Priority_Queue(2)
q.insert('hey', 0)
q.insert('last', 0)
assert q.pop() == 'hey'
assert q.pop() == 'last'
def populated_queue():
pq = Priority_Queue()
pq.insert(PNode(100, 10))
pq.insert(PNode(150, 1))
pq.insert(PNode("Hello", 30))
pq.insert(PNode("first_2000", 2000))
pq.insert(PNode("second_2000", 2000))
return pq
def pop_off_empty_queue():
pq = Priority_Queue()
with pytest.raises(IndexError):
pq.pop()
def test_insert_into_empty_queue():
pq = Priority_Queue()
pq.insert(PNode("thirty", 30))
assert pq.peek() == "thirty"
def m_eq(request):
return Priority_Queue(2)
def populated_queue():
pq = Priority_Queue()
pq.insert(PNode(100, 10))
pq.insert(PNode(150, 1))
pq.insert(PNode("Hello", 30))
pq.insert(PNode("first_2000", 2000))
pq.insert(PNode("second_2000", 2000))
return pq
def pop_off_empty_queue():
pq = Priority_Queue()
with pytest.raises(IndexError):
pq.pop()
def test_insert_into_empty_queue():
pq = Priority_Queue()
pq.insert(PNode('thirty', 30))
assert pq.peek() == 'thirty'