“Great!” Exclaimed Sofia. “Now we have the password.”

“To what exactly?” Quipped Nikola.

“Untold treasures, vast riches beyond belief! Gold! Silver! Silicon! Hydraulic Fluid! Anything your heart desires!”

“And you’re going to do what with a password to absolutely nothing?” Nikola smirked.

“Oh... Right...”

Stephen spoke up. “Well, this door back here has a keypad. Only thing is the brackets look pretty busted up. We could try fixing it and then punching in the password?”

“YES! That!” Sofia exclaimed.

You are given an expression with numbers, brackets and operators. For this task only the brackets matter. Brackets come in three flavors: "{}" "()" or "[]". Brackets are used to determine scope or to restrict some expression. If a bracket is open, then it must be closed with a closing bracket of the same type. The scope of a bracket must not intersected by another bracket. In this task you should make a decision, whether to correct an expression or not based on the brackets. Do not worry about operators and operands.

Input: An expression with different of types brackets as a string (str).

Output: A verdict on the correctness of the expression as logic value (bool).


assert checkio("((5+3)*2+1)") == True
assert checkio("{[(3+1)+2]+}") == True
assert checkio("(3+{1-1)}") == False
assert checkio("[1+1]+(2*2)-{3/3}") == True

How it is used: When you write code or complex expressions in a mathematical package, you can get a huge headache when it comes to excess or missing brackets. This concept can be useful for your own IDE.


  • There are only brackets ("{}" "()" or "[]"), digits or operators ("+" "-" "*" "/");
  • 0 < len(expression) < 103.

Invalid hot key. Each hot key should be unique and valid
Hot keys:
CheckiO Extensions

CheckiO Extensions allow you to use local files to solve missions. More info in a blog post.

In order to install CheckiO client you'll need installed Python (version at least 3.8)

Install CheckiO Client first:

pip3 install checkio_client

Configure your tool

checkio --domain=py config --key=

Sync solutions into your local folder

checkio sync

(in beta testing) Launch local server so your browser can use it and sync solution between local file end extension on the fly. (doesn't work for safari)

checkio serv -d

Alternatevly, you can install Chrome extension or FF addon

checkio install-plugin
checkio install-plugin --ff
checkio install-plugin --chromium

Read more here about other functionality that the checkio client provides. Feel free to submit an issue in case of any difficulties.

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