class PseudoQueue:
def __init__(self):
self.stack_to_enqueue = Stack()
self.stack_to_dequeue = Stack()
def enqueue(self, new_val, *args):
while not self.stack_to_dequeue.isEmpty():
self.stack_to_enqueue.push(self.stack_to_dequeue.pop())
self.stack_to_enqueue.push(new_val, *args)
return
def dequeue(self):
while not self.stack_to_enqueue.isEmpty():
self.stack_to_dequeue.push(self.stack_to_enqueue.pop())
if self.stack_to_dequeue.isEmpty():
raise RuntimeError("cannot dequeue from empty queue")
return self.stack_to_dequeue.pop()
def __str__(self):
""" { a } -> { b } -> { c } -> NULL """
final_string = ""
while not self.stack_to_dequeue.isEmpty():
self.stack_to_enqueue.push(self.stack_to_dequeue.pop())
current = self.stack_to_enqueue.top
while current:
final_string += f" <-- {{{current.value}}} "
current = current.next
return f"NULL{final_string}"
def matching_brackets(string):
bracket = Stack()
bracket_dict = {"(": ")", "{": "}", "[": "]"}
for char in string:
if char in bracket_dict:
bracket.push(char)
elif char in [")", "}", "]"]:
if bracket.isEmpty():
return False
if bracket_dict[bracket.peek()] == char:
bracket.pop()
else:
return False
if not bracket.isEmpty():
return False
return True
def is_palindrome(ll):
mid = ll.head
scout = ll.head
pal = Stack()
# get the stack set up
while scout.next:
pal.push(mid.value)
if scout.next.next:
scout = scout.next.next
mid = mid.next
else:
break
mid = mid.next
while mid:
if mid.value == pal.peek():
pal.pop()
mid = mid.next
else:
return False
return True
def graph_depth_first(self, vertex):
if vertex not in self.get_vertices():
return f"{vertex} is not in graph"
vertex_stack = Stack()
visited_list = [vertex]
vertex_stack.push(vertex)
while not vertex_stack.isEmpty():
new_vertex = vertex_stack.peek()
new_vertex_neighbors = self.get_neighbors(new_vertex)
counter = 0
for edge in new_vertex_neighbors:
vert, wt = edge.split(" ")
if vert not in visited_list:
vertex_stack.push(vert)
visited_list.append(vert)
counter += 1
if counter == 0:
vertex_stack.pop()
return visited_list
def multi_bracket_validation(input_string):
br_dict = {'}': '{', ')': "(", ']': "["}
if input_string == "":
return False
_stack = Stack()
_stack_length = 0
for chr in input_string:
if chr in br_dict:
if br_dict[chr] == _stack.peek():
_stack.pop()
else:
return False
elif chr in br_dict.values():
_stack.push(chr)
_stack_length += 1
if _stack_length == 0:
return "no brackets in string"
elif _stack.isEmpty():
return True
return False
def test_Stack_push_newValue():
fruit = Stack()
fruit.push("apples")
actual = str(fruit)
expected = "{apples} -> NULL"
assert actual == expected
def fruit_stack():
fruit_stack = Stack()
fruit_stack.push("apples")
fruit_stack.push("bananas")
return fruit_stack