Validating Balanced Brackets | Dataford Interview Questions

AI-first Technology's prompt editor must reject prompts containing incorrectly matched brackets before they are sent for processing. Given a string representing a prompt, determine whether every bracket is correctly opened, closed, and nested.

The supported bracket pairs are (), [], and {}. All other characters, including letters, digits, whitespace, and operators, must be ignored. A prompt is balanced only when each closing bracket matches the most recently opened bracket and no brackets remain unclosed.

Formal Specification

Implement is_balanced(expression).

Input: expression, a string of length n containing printable characters.
Output: Return True if all brackets are balanced and properly nested; otherwise return False.

Constraints

0 <= len(expression) <= 10^5
The string may contain any printable ASCII characters
Only (), [], and {} are bracket characters
An empty string is considered balanced

Function Signature

def is_balanced(expression):

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