Valid Parentheses | Dataford Interview Questions

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Problem

Raptive configuration tools may process strings containing grouping delimiters such as parentheses, brackets, and braces. Given a string, determine whether every opening delimiter is closed by the correct type in the correct order.

Return True if the string is valid, and False otherwise. All non-delimiter characters should be ignored.

Formal Specification

Implement is_valid(s), where s is a string. The function returns a boolean:

An opening delimiter (, [, or { must be closed by the matching delimiter.
Delimiters must close in last-in, first-out order.
Every closing delimiter must have a corresponding earlier opening delimiter.
Non-delimiter characters do not affect validity.

Constraints

0 <= len(s) <= 10^4
s contains printable ASCII characters
Valid delimiter pairs are (), [], and {}

Function Signature

def is_valid(s):