Making Change

Making Change


Nicola is taking a much needed vacation. He'll be backpacking around some lesser-known countries. Each has its own unique currency.

When making purchases, Nicola would like to use the minimum number of coins possible. For example, Outer Leftopia has coins with denomination 1, 3, and 5 shillings. He wants to buy a souvenir that costs 13 shillings. He can do that using two 5 shilling coins and one 3 shilling coin.

You can assume Nicola has access to an infinite number of coins of each denomination. (He has a large bank account and access to an ATM).

Input: Two arguments. The first argument is an int: the price of the purchase. The second is a list of ints: the denominations of available coins.

Output: int. The minimum number of coins Nicola can use to make the purchase. If the price cannot be made with the available denominations, return None.


checkio(8, [1, 3, 5]) == 2
checkio(12, [1, 4, 5]) == 3

How it is used: Besides helping Nicola make change, this is an example of a problem in combinatorial optimization.

Precondition: Inputs are all positive integers.

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.

Pair Programming (Beta-version)

Welcome to Pair Programming! Engage in real-time collaboration on coding projects by starting a session and sharing the provided unique URL with friends or colleagues. This feature is perfect for joint project development, debugging, or learning new skills together. Simply click 'Start Session' to begin your collaborative coding journey!

Waiting for Pair Programming to start...

You are trying to join a pair programming session that has not started yet.

Please wait for the session creator to join.

Waiting for Pair Programming to reconnect...

It looks like the creator of the pair programming session closed the editor window.

It might happen accidentally, so that you can wait for reconnection.

<< <
> >>
exec show

Whats Next?

Free accounts will see Best CheckiO solutions with some delay.
Best Solutions will be opened in a moment
Become Awesome and Don't wait
The next stage is ""
Will be activated in
View More Solutions Random Review Solutions Go to the next mission