Bracket Inspector

Story

Your editor plugin must decide, before it reformats a file, whether the brackets in a snippet are properly nested. A single stray ) or a ] closing a ( means the formatter must refuse to touch the file.

Task

Write a function that returns whether a string is balanced:

• the bracket pairs are (), [] and {};
• every opening bracket must be closed by a bracket of the same type, and brackets must close in the reverse order they were opened;
• every other character (letters, digits, spaces, quotes…) is ignored and has no special meaning;
• the empty string is balanced.

Strings are at most 10 000 characters long, so a recursive solution can run out of stack: prefer a loop.

Function to implement

| Language | Signature | |---|---| | Python | def is_balanced(s: str) -> bool | | JavaScript | function isBalanced(s) returning true or false |

A hidden driver calls your function once per test string and prints yes or no. Do not read input or print anything yourself: just define the function (helper functions are fine).

Example

is_balanced("([]{})")   ->  True
is_balanced("a(b)c[d]") ->  True
is_balanced("(]")       ->  False   (wrong type)
is_balanced("([)]")     ->  False   (wrong order)
is_balanced("((")       ->  False   (never closed)
is_balanced("")         ->  True