def multi_bracket_validation(input):
'''
Input: string Output: boolean stating True if brackets are balanced in the input string
'''
bracket_tower = Stack()
for char in input:
if char in ['(', '[', '{']:
bracket_tower.push(char)
elif char in [')', ']', '}']:
if bracket_tower.is_empty():
return False
removed_char = bracket_tower.pop()
if char == ')' and removed_char != '(':
return False
elif char == ']' and removed_char != '[':
return False
elif char == '}' and removed_char != '{':
return False
if bracket_tower.is_empty():
return True
return False
def test_check_not_empty():
s = Stack()
s.push("apple")
s.push("banana")
actual = s.is_empty()
expected = False
assert actual == expected
class PseudoQueue:
'''
This PseudoQueue class definition can be used to create an instance of a queue data strucsture. It will be composed of nodes and has the methods of enqueue, dequeue, is_empty, and peek. It has attritubes of rear and front. As an additional challenge... this class of PseudoQueues uses two stacks at its implementation layer.
'''
def __init__(self):
self.front_stack = Stack()
self.rear_stack = Stack()
self.front = self.rear = None
def enqueue(self, value=None):
node = Node(value)
if self.rear_stack.top:
self.rear_stack.top.next_node = node
self.rear_stack.top = node
if not self.front_stack.top:
self.front_stack.top = node
self.front = self.front_stack.top
def is_empty(self):
return self.front_stack.is_empty()
def dequeue(self, ):
if self.front_stack.top == self.rear_stack.top:
self.rear_stack.top = None
value = self.front_stack.pop()
print("front stack top is:")
return value
def peek(self):
return self.front_stack.peek()
def test_pop_until_empty():
s = Stack()
s.push("apple")
s.push("banana")
s.push("cucumber")
s.pop()
s.pop()
s.pop()
actual = s.is_empty()
expected = True
assert actual == expected
def test_pop_to_empty():
stck2 = Stack()
stck2.push(9)
stck2.push(8)
stck2.push(10)
stck2.push(11)
stck2.pop()
stck2.pop()
stck2.pop()
stck2.pop()
assert stck2.top == None
assert stck2.is_empty() == True
def depth_first(self, start):
visited = []
s = Stack()
s.push(start)
visited.append(start)
while s.is_empty() == False:
curr = s.peek()
flag = False
for neighbor in self.get_neighbors(curr):
if neighbor[0] not in visited and flag == False:
s.push(neighbor[0])
visited.append(neighbor[0])
flag = True
if flag == False:
s.pop()
return visited
def test_stack_is_empty():
stack6 = Stack()
assert stack6.is_empty() == True
stack6.push(5)
assert stack6.is_empty() == False
def test_pop_from_empty():
stck = Stack()
assert stck.is_empty() == True
with pytest.raises(AttributeError):
stck.peek()
def test_instantiate_empty_stack():
stck = Stack()
assert stck.top == None
assert stck.is_empty() == True
