def test_stack3(self):
stack = StackLinkedList()
self.assertTrue(stack.is_empty())
stack.push(1)
self.assertFalse(stack.is_empty())
item = stack.pop()
self.assertEqual(item, 1)
def test_stack(self):
# initialize an object
s = StackLinkedList()
self.assertEqual(s.is_empty(), True)
def __init__(self, infix):
self.tokens = infix.split()
self.opStack = StackLinkedList()
self.valStack = StackLinkedList()
self.parentheses = 0
def test_stack2(self):
# initialize an object
s = StackLinkedList()
s.push(1)
self.assertEqual(s.is_empty(), False)
class DijkstraTwoStack:
def __init__(self, infix):
self.tokens = infix.split()
self.opStack = StackLinkedList()
self.valStack = StackLinkedList()
self.parentheses = 0
def process_token(self, s):
if s == "(":
self.parentheses += 1
elif s == ")":
self.parentheses -= 1
self.operate()
elif s in "+ - * / ^ %".split():
self.opStack.push(s)
else:
n = int(s)
self.valStack.push(n)
def operate(self):
y = self.valStack.pop()
x = self.valStack.pop()
if self.opStack.peek() == "+":
self.valStack.push(x + y)
self.opStack.pop()
return
elif self.opStack.peek() == "-":
self.valStack.push(x - y)
self.opStack.pop()
return
elif self.opStack.peek() == "*":
self.valStack.push(x * y)
self.opStack.pop()
return
elif self.opStack.peek() == "/":
self.valStack.push(x / y)
self.opStack.pop()
return
else:
raise BqsException(
f"operator not recognized: {self.opStack.peek()}")
def evaluate(self):
for i in self.tokens:
self.process_token(i)
if self.parentheses != 0:
raise BqsException(
f"there are {self.parentheses} superfluous parentheses (net)")
while not self.opStack.is_empty():
self.operate()
result = self.valStack.pop()
if not self.valStack.is_empty():
raise BqsException("there are superfluous values")
return result