def infix2prefix(expression):
res_stack = LinkedStack()
op_stack = LinkedStack()
op_priority = {'*': 2, '/': 2, '%': 2, '+': 1, '-': 1, '(': 0, ')': 0}
width = 7 if len(expression) <= 7 else len(expression)
print(expression[::-1])
print('Symbol'.center(8),
'op_stack'.center(width),
'res_stack'.center(width),
sep=" | ")
print('-' * (width * 3 + 7))
for e in reversed(expression):
if e == ')':
op_stack.push(e)
elif e == '(':
while op_stack.first() != ')':
res_stack.push(op_stack.pop())
op_stack.pop()
elif e.isdigit():
res_stack.push(e)
else:
while op_stack.first(
) and op_priority[e] <= op_priority[op_stack.first()]:
res_stack.push(op_stack.pop())
op_stack.push(e)
print_stack(e, op_stack, res_stack, width)
while not op_stack.is_empty():
res_stack.push(op_stack.pop())
print_stack(' ', op_stack, res_stack, width)
output = ''
while not res_stack.is_empty():
output += res_stack.pop()
return output
def infix2postfix(expression):
output = []
op_stack = LinkedStack()
op_priority = {'*': 2, '/': 2, '%': 2, '+': 1, '-': 1, '(': 0, ')': 0}
for e in expression:
if e == '(':
op_stack.push(e)
elif e == ')':
while op_stack.first() != '(':
output.append(op_stack.pop())
op_stack.pop()
elif e.isdigit():
output.append(e)
else:
while not op_stack.is_empty() and op_priority[op_stack.first()] >= op_priority[e]:
output.append(op_stack.pop())
op_stack.push(e)
while not op_stack.is_empty():
output.append(op_stack.pop())
return ''.join(output)