def test_stack_push_one():
value = 1
stack = Stack()
stack.push(value)
actual = stack.top.value
expected = value
assert actual == expected
class PseudoQueue:
def __init__(self, stack1):
self.stack1 = Stack()
self.stack2 = Stack()
def enqueue(self, value):
self.stack1.push(value)
def dequeue(self):
if self.stack1.top == None:
raise EmptyQueueException()
while self.stack1.top != None:
popped_value = self.stack1.pop()
self.stack2.push(popped_value)
stack2_popped = self.stack2.pop()
while self.stack2.top != None:
self.stack1.push(self.stack2.pop())
return stack2_popped
def peek(self):
return self.stack1.peek()
def test_stack_peek():
value = 1
node = Node(value)
stack = Stack(node)
actual = stack.peek()
expected = value
assert actual == expected
def test_stack_pop():
value1 = 1
value2 = 2
stack = Stack()
stack.push(value1)
stack.push(value2)
actual = stack.pop()
expected = value2
assert actual == expected
def test_stack_push_many():
value1 = 1
value2 = 2
stack = Stack()
stack.push(value1)
stack.push(value2)
actual = stack.top.value
expected = value2
assert actual == expected
class Pseudoqueue:
def __init__(self):
self.back = Stack()
self.front = Stack()
def enqueue(self, value):
print("pushing ", value)
try:
while self.front.top != None:
self.back.push(self.front.pop())
# print('xxxx')
# print(self.back.top.value)
# print(self.back.top.next)
except AttributeError:
print('Front is Empty')
self.back.push(value)
# print(self.back.top.value)
try:
while self.back.top != None:
# print(self.back.top.value)
self.front.push(self.back.pop())
# print('-----------')
except AttributeError:
print('Back is Empty')
# print('top: ', self.front.top.value)
def dequeue(self):
return self.front.pop()
def test_pop_when_multiple():
stack = Stack()
stack.push(1)
stack.push(2)
stack.push(3)
stack.pop()
stack.pop()
actual = stack.pop()
expected = 1
assert actual == expected
def test_push_onto_full():
s = Stack()
s.push("apple")
s.push("banana")
s.push("cucumber")
actual = s.top.value
expected = "cucumber"
assert actual == expected
def test_pseudoqueue_dequeue_multiple():
testing_queue = PseudoQueue(Stack())
testing_queue.enqueue(1)
testing_queue.enqueue(2)
testing_queue.dequeue()
expected = 2
actual = testing_queue.peek()
assert actual == expected
def test_peek():
s = Stack()
s.push("apple")
s.push("banana")
actual = s.peek()
expected = "banana"
assert actual == expected
def test_check_not_empty():
s = Stack()
s.push("apple")
s.push("banana")
actual = s.is_empty()
expected = False
assert actual == expected
def test_is_empty():
stack = Stack()
stack.push(1)
stack.pop()
actual = stack.is_empty()
expected = True
assert actual == expected
def multi_bracket_validation(input: str) -> bool:
"""Check if the passed string has matching pairs of brackets
Args:
input (str): String to be checked
Returns:
bool: Whether or not the brackets match
"""
br_stack = Stack()
brackets = {
')': '(',
']': '[',
'}': '{',
}
for char in input:
# Add opening bracket to the stack
if char in brackets.values():
br_stack.push(char)
# Check if closing bracket matches the most recent opening
elif char in brackets.keys():
try:
if not brackets[char] == br_stack.pop():
return False
except AttributeError as err:
print(err)
return False
return br_stack.is_empty()
def test_push_multiple():
stack = Stack()
stack.push(1)
stack.push(2)
stack.push(3)
actual = stack.top.value
expected = 3
assert actual == expected
def test_stack_pop_until_empty():
value1 = 1
value2 = 2
stack = Stack()
stack.push(value1)
stack.push(value2)
stack.pop()
stack.pop()
actual = stack.top
expected = None
assert actual == expected
def test_stack_new_empty():
stack = Stack()
actual = stack.top
expected = None
assert actual == expected
def test_instantiate_stack():
stack = Stack()
assert stack.top == None
def test_pop_one():
stack = Stack()
stack.push(1)
actual = stack.pop()
expected = 1
assert actual == expected
def test_push_multiple_fails():
stack = Stack()
stack.push(1)
stack.push(2)
stack.push(3)
assert stack.top.value != 2
def test_push_onto_stack_not_none():
stack = Stack()
stack.push(1)
assert stack.top.value != None
def test_push_onto_stack():
stack = Stack()
stack.push(1)
actual = stack.top.value
expected = 1
assert actual == expected
def __init__(self):
self.back = Stack()
self.front = Stack()
class PseudoQueue:
"""Queue that uses two stacks"""
def __init__(self):
"""Method initializer
"""
self.add = Stack()
self.remove = Stack()
def __len__(self):
return len(self.add) + len(self.remove)
def enqueue(self, val):
"""Add a new element ot the queue
Args:
val (any): Value to be added
Returns:
any: Value that was added to the queue
"""
try:
while self.remove.peek():
self.add.push(self.remove.pop())
except AttributeError as err:
pass
self.add.push(val)
return self.add.top.val
def dequeue(self):
"""Remove the first element from the queue and return its value
Raises:
AttributeError: When the method is called on the empty queue
Returns:
any: Value of the removed element
"""
try:
while self.add.peek():
self.remove.push(self.add.pop())
except AttributeError as err:
pass
try:
return self.remove.pop()
except AttributeError as err:
raise AttributeError('Cannot be called on empty queue')
def test_peek():
stack = Stack()
stack.push(1)
actual = stack.peek()
expected = 1
assert actual == expected
def test_raise_exception_when_popping():
stack = Stack()
with pytest.raises(InvalidOperationError) as e:
stack.pop()
assert str(e.value) == "Popping from an empty stack!"
def test_stack_peek_empty_exception():
stack = Stack()
with pytest.raises(Exception):
stack.peek()
def __init__(self, stack1):
self.stack1 = Stack()
self.stack2 = Stack()
class AnimalShelter:
def __init__(self):
self.main_stack = Stack()
self.helper_stack = Stack()
def enqueue(self, animal):
while not isinstance(self.main_stack.peek(), EmptyStackException):
self.helper_stack.push(self.main_stack.pop())
self.helper_stack.push(animal)
while not isinstance(self.helper_stack.peek(), EmptyStackException):
self.main_stack.push(self.helper_stack.pop())
def dequeue(self, animal):
if isinstance(self.main_stack.peek(), EmptyStackException):
return EmptyStackException()
saved_animal = None
while not isinstance(self.main_stack.peek(), EmptyStackException):
if not saved_animal and isinstance(self.main_stack.peek(), animal):
saved_animal = self.main_stack.pop()
else:
self.helper_stack.push(self.main_stack.pop())
while not isinstance(self.helper_stack.peek(), EmptyStackException):
self.main_stack.push(self.helper_stack.pop())
return saved_animal
def peek(self):
return self.main_stack.peek()
def __init__(self):
"""Method initializer
"""
self.add = Stack()
self.remove = Stack()
def __init__(self):
self.main_stack = Stack()
self.helper_stack = Stack()
