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39 lines
1.1 KiB
Python
39 lines
1.1 KiB
Python
from .stack import Stack
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def balanced_parentheses(parentheses: str) -> bool:
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"""Use a stack to check if a string of parentheses is balanced.
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>>> balanced_parentheses("([]{})")
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True
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>>> balanced_parentheses("[()]{}{[()()]()}")
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True
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>>> balanced_parentheses("[(])")
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False
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>>> balanced_parentheses("1+2*3-4")
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True
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>>> balanced_parentheses("")
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True
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"""
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stack: Stack[str] = Stack()
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bracket_pairs = {"(": ")", "[": "]", "{": "}"}
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for bracket in parentheses:
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if bracket in bracket_pairs:
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stack.push(bracket)
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elif bracket in (")", "]", "}") and (
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stack.is_empty() or bracket_pairs[stack.pop()] != bracket
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):
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return False
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return stack.is_empty()
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if __name__ == "__main__":
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from doctest import testmod
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testmod()
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examples = ["((()))", "((())", "(()))"]
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print("Balanced parentheses demonstration:\n")
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for example in examples:
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not_str = "" if balanced_parentheses(example) else "not "
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print(f"{example} is {not_str}balanced")
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