This is a follow-up for here, for bug fixes and applied advice.
Your friend John uses a lot of emoticons when you talk to him on Messenger. In addition to being a person who likes to express himself through emoticons, he hates unbalanced parenthesis so much that it makes him go :(
Sometimes he puts emoticons within parentheses, and you find it hard to tell if a parenthesis really is a parenthesis or part of an emoticon.
A message has balanced parentheses if it consists of one of the following:
- An empty string ""
- One or more of the following characters: 'a' to 'z', ' ' (a space) or ':' (a colon)
- An open parenthesis '(', followed by a message with balanced parentheses, followed by a close parenthesis ')'.
- A message with balanced parentheses followed by another message with balanced parentheses.
- A smiley face ":)" or a frowny face ":("
- Write a program that determines if there is a way to interpret his message while leaving the parentheses balanced.
I'm working on this balanced smileys checking algorithm, and my current solution is very naive, with just two rules:
- At any point, the number of
)(close) should be less than the number of
((open) + number of
- At the end, the number of
((open) should be less than the number of
I'm wondering if there are any bugs in my checking logic. Any advice on algorithm time complexity improvement or code style advice is highly appreciated as well.
def check_balance(source): left = 0 right = 0 smile = 0 # :) frown = 0 # :( pre = '' for c in source: if c == ')': if pre == ':': smile += 1 else: right += 1 if right > left + frown: return False elif c == '(': if pre == ':': frown += 1 else: left += 1 pre = c if left > right + smile: return False return True if __name__ == "__main__": raw_smile_string = 'abc(b:)cdef(:()' # true raw_smile_string = 'a)' # false raw_smile_string = ')(' # false print check_balance(raw_smile_string)