Valid Parentheses

Python data engineering interview problem. Difficulty: beginner. Pattern: Stacks. About 10 minutes. Free to practice.

Check whether brackets are correctly matched and nested. Treat this as a production helper: match the contracted return shape, including empty and duplicate inputs.

Code, math and configuration files use brackets that come in pairs: (), [] and {}. A bracket that is opened must be closed, in the right order, by the same kind of bracket. Write a function valid_parentheses(s) that takes a string made only of these 6 characters and returns True if the brackets are balanced, otherwise False. A string is valid when every opening bracket is closed by the same type of bracket, and brackets close in the correct order. '()[]{}' is valid. '(]' is not valid, because ( is closed by the wrong kind of bracket. '([)]' is not valid either, because the brackets cross each other. Keep the print lines in the editor.

Requirements

• Return True only if every bracket is closed by the right type.
• Brackets must close in the correct order. The most recently opened one must be closed first.
• Return False if some bracket is never closed or if a closing bracket has no opening one.
• An empty string is valid.

Constraints

• The string only contains the characters (, ), [, ], { and }.
• The result is a Python True or False.

Examples

Input: valid_parentheses('()[]{}') Output: True Each close matches the latest open.

Topics: lakebench, python, stack, brackets.

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