mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-12-21 10:40:14 +00:00
17059b7ece
* Added doctests , type hints * Update nested_brackets.py --------- Co-authored-by: Christian Clauss <cclauss@me.com>
74 lines
1.8 KiB
Python
74 lines
1.8 KiB
Python
"""
|
|
The nested brackets problem is a problem that determines if a sequence of
|
|
brackets are properly nested. A sequence of brackets s is considered properly nested
|
|
if any of the following conditions are true:
|
|
|
|
- s is empty
|
|
- s has the form (U) or [U] or {U} where U is a properly nested string
|
|
- s has the form VW where V and W are properly nested strings
|
|
|
|
For example, the string "()()[()]" is properly nested but "[(()]" is not.
|
|
|
|
The function called is_balanced takes as input a string S which is a sequence of
|
|
brackets and returns true if S is nested and false otherwise.
|
|
"""
|
|
|
|
|
|
def is_balanced(s: str) -> bool:
|
|
"""
|
|
>>> is_balanced("")
|
|
True
|
|
>>> is_balanced("()")
|
|
True
|
|
>>> is_balanced("[]")
|
|
True
|
|
>>> is_balanced("{}")
|
|
True
|
|
>>> is_balanced("()[]{}")
|
|
True
|
|
>>> is_balanced("(())")
|
|
True
|
|
>>> is_balanced("[[")
|
|
False
|
|
>>> is_balanced("([{}])")
|
|
True
|
|
>>> is_balanced("(()[)]")
|
|
False
|
|
>>> is_balanced("([)]")
|
|
False
|
|
>>> is_balanced("[[()]]")
|
|
True
|
|
>>> is_balanced("(()(()))")
|
|
True
|
|
>>> is_balanced("]")
|
|
False
|
|
>>> is_balanced("Life is a bowl of cherries.")
|
|
True
|
|
>>> is_balanced("Life is a bowl of che{}ies.")
|
|
True
|
|
>>> is_balanced("Life is a bowl of che}{ies.")
|
|
False
|
|
"""
|
|
open_to_closed = {"{": "}", "[": "]", "(": ")"}
|
|
stack = []
|
|
for symbol in s:
|
|
if symbol in open_to_closed:
|
|
stack.append(symbol)
|
|
elif symbol in open_to_closed.values() and (
|
|
not stack or open_to_closed[stack.pop()] != symbol
|
|
):
|
|
return False
|
|
return not stack # stack should be empty
|
|
|
|
|
|
def main():
|
|
s = input("Enter sequence of brackets: ")
|
|
print(f"'{s}' is {'' if is_balanced(s) else 'not '}balanced.")
|
|
|
|
|
|
if __name__ == "__main__":
|
|
from doctest import testmod
|
|
|
|
testmod()
|
|
main()
|