def infix_to_postfix(expression):
operator_stack = Stack()
output = []
token_list = expression.split()
precedence = {"^": 4, "*": 3, "/": 3, "+": 2, "-": 2, "(": 1}
chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
for token in token_list:
try:
int(token)
number = True
except ValueError:
number = False
if token in chars or number:
output.append(token)
elif token == "(":
operator_stack.add(token)
elif token == ")":
stack_token = operator_stack.pop()
while stack_token != "(":
output.append(stack_token)
stack_token = operator_stack.pop()
else:
while (not operator_stack.is_empty()) and \
(precedence[operator_stack.peek()] >= precedence[token]):
output.append(operator_stack.pop())
operator_stack.add(token)
while not operator_stack.is_empty():
output.append(operator_stack.pop())
return " ".join(output)
def base_converter(number, base):
num_stack = Stack()
values = "0123456789ABCDEFGHIJKLMOPQ"
while number > 0:
num_stack.add(number % base)
number = number // base
converted_number = ""
while not num_stack.is_empty():
converted_number += values[num_stack.pop()]
return converted_number
def build_parse_tree(fp_exp):
fp_list = fp_exp.split()
p_stack = Stack()
e_tree = BinaryTree('')
p_stack.add(e_tree)
current_tree = e_tree
for i in fp_list:
if i == '(':
current_tree.insert_left('')
p_stack.add(current_tree)
current_tree = current_tree.get_left_child()
elif i not in ['+', '-', '*', '/', ')']:
current_tree.set_root_val(int(i))
parent = p_stack.pop()
current_tree = parent
elif i in ['+', '-', '*', '/']:
current_tree.set_root_val(i)
current_tree.insert_right('')
p_stack.add(current_tree)
current_tree = current_tree.get_right_child()
elif i == ')':
current_tree = p_stack.pop()
else:
raise ValueError
return e_tree