def rpn(expression):
# operand: sayi
# operation: islem
operations = ['+', '*', '-', '/']
elements = expression.split()
stack = MyStack()
for e in elements:
if e in operations:
num2 = stack.pop()
num1 = stack.pop()
if e == '+':
result = num1 + num2
elif e == '*':
result = num1 * num2
elif e == '-':
result = num1 - num2
else:
result = num1 / num2
stack.push(result)
else:
num = int(e)
stack.push(num)
print(stack.pop())
def test_is_empty(self):
stack = MyStack()
self.assertTrue(stack.is_empty())
stack.push(1)
self.assertFalse(stack.is_empty())
stack.pop()
self.assertTrue(stack.is_empty())
class MyQueue():
""" Queue implementation using 2 stacks """
def __init__(self):
self.latest = MyStack()
self.oldest = MyStack()
def __len__(self):
# Data in Queue should always be in one of the two internal stacks
len_latest, len_oldest = len(self.latest), len(self.oldest)
if (len_latest > len_oldest):
return len_latest
return len_oldest
def is_empty(self):
return self.latest.is_empty() and self.oldest.is_empty()
def move(self, from_stack, to_stack):
""" Move top element from from_stack (pop) onto to_stack (push) """
to_stack.push(from_stack.pop())
def push(self, data):
while (self.oldest.is_empty() != True):
self.move(self.oldest, self.latest)
self.latest.push(data)
def pop(self):
while (self.latest.is_empty() != True):
self.move(self.latest, self.oldest)
return self.oldest.pop()
class TestMyStack(unittest.TestCase):
def setUp(self):
# Provide an empty stack
self.stack = MyStack()
# Provide a filled stack
self.len_test_data = 5
self.test_data = [i + 1 for i in range(self.len_test_data)]
self.filled_stack = MyStack()
for i in self.test_data:
self.filled_stack.push(i)
def test_instantiation(self):
stack = MyStack()
self.assertEqual(None, stack.top)
self.assertEqual(0, len(self.stack))
def test_push(self):
for i in self.test_data:
self.stack.push(i)
self.assertEqual(i, len(self.stack))
self.assertEqual(i, self.stack.top.key)
def test_pop(self):
for i in reversed(self.test_data):
data = self.filled_stack.pop()
self.assertEqual(i - 1, len(self.filled_stack))
self.assertEqual(i, data)
def test_peek(self):
for i in reversed(self.test_data):
data = self.filled_stack.peek()
self.assertEqual(i, data)
self.filled_stack.pop()
def test_is_empty(self):
stack = MyStack()
self.assertTrue(stack.is_empty())
stack.push(1)
self.assertFalse(stack.is_empty())
stack.pop()
self.assertTrue(stack.is_empty())