def test_pushMultiple_ComeOutFILO(self):
stack = Stack()
stack.push(2)
stack.push(1)
out1 = stack.pop()
out2 = stack.pop()
self.assertEqual(1, out1)
self.assertEqual(2, out2)
class MyQueue:
def __init__(self):
self.s1 = Stack() # Use for dequeues
self.s2 = Stack() # Use for reverse ordering
def enqueue(self, item):
#while not self.s1.is_empty():
while self.s1.peek() is not None:
self.s2.push(self.s1.pop())
self.s2.push(item)
#while not self.s2.is_empty():
while self.s2.peek() is not None:
self.s1.push(self.s2.pop())
def dequeue(self):
return self.s1.pop()
def __str__(self):
return "s1: {}\ns2: {}".format(self.s1.__str__(), self.s2.__str__())
class MyQueue:
""" For Question 5. """
def __init__(self):
self.s1 = Stack()
self.s2 = Stack()
def enqueue(self, item):
""" Add to end. """
self.s1.push(item)
def dequeue(self):
""" Remove from front. """
if self.s1.is_empty():
return None
while (not self.s1.is_empty()):
self.s2.push( self.s1.pop() )
result = self.s2.pop()
while (not self.s2.is_empty()):
self.s1.push( self.s2.pop() )
return result
class QueueViaStack(object):
'''
Time :
Space:
Note :
'''
def __init__(self):
self.input = Stack()
self.output = Stack()
def push(self, data):
self.input.push(data)
def pop(self):
if self.input.empty() and self.output.empty():
return None
curr = self.input.pop()
while curr != None:
self.output.push(curr.data)
curr = self.input.pop()
return self.output.pop()
def sort_stack(s):
assert not s.is_empty()
ss = Stack() # This will be the auxiliary stack
num_elements = 0
while not s.is_empty():
ss.push(s.pop())
num_elements += 1
num_sorted = 0
while num_sorted < num_elements:
# `num_sorted` is how much `s` is filled.
# `ss` has the `num_elements-num_sorted` elements.
min_item = np.float('inf')
# Search through all non-sorted items to find minimum.
for _ in range(num_elements - num_sorted):
item = ss.pop()
if item < min_item:
min_item = item
s.push(item)
# Put all unsorted items other than the one with min back
# into ss, if we get the min hold it out and put it in s.
got_min = False # Handle duplicates
for _ in range(num_elements - num_sorted):
item = s.pop()
if item == min_item and not got_min:
got_min = True
else:
ss.push(item)
s.push(min_item)
num_sorted += 1
return s
def test_canPushAndPop(self):
stack = Stack()
stack.push(1)
out = stack.pop()
self.assertEqual(1, out)
