def test_push():
my_stack = Stack()
my_stack.push(0)
my_stack.push(1)
assert my_stack.items == [0, 1]
assert my_stack.size() == 2
assert my_stack.is_empty() is False
def parens_matched(x):
# Read a string from left to right and decide whether left and right parentheses are balanced.
stack = Stack()
matched = True
for char in x:
if char == '(':
stack.push(0)
elif char == ')':
popped = stack.pop()
if popped == []:
matched = False
break
return matched and stack.size() == 0
def convert_infix_to_postfix(infix_expr):
op = Stack()
postfix = []
infix = list(infix_expr)
for index in range(len(infix)):
if infix[index] in ops:
while (not op.is_empty()) and precedence[op.peek()] >= precedence[infix[index]]:
if op.peek() == '(':
op.pop()
else:
postfix.append(op.pop())
if infix[index] != ')':
op.push(infix[index])
elif infix[index] != ' ':
postfix.append(infix[index])
while op.size() > 0:
postfix.append(op.pop())
print(''.join(postfix))
def test_initialization():
my_stack = Stack()
assert my_stack.items == []
assert my_stack.size() == 0
assert my_stack.is_empty()
