Console-based implementation of the Countdown numbers game.
Countdown is a popular game show in the UK. This is my take on it.
You will be given 6 numbers and a goal number.
Your task: Use the 6 numbers to get as close to the goal number as possible.
You may add, subtract, multiply, and divide the given numbers, but the result MUST be an integer. You don't have to use all of the numbers, but you can't use any numbers that haven't been given. The order of the numbers in your answer does not matter.
Give your solution as an algebraic expression (e.g. 5 * 6 + 9). You may use parentheses.
Your cards are [3, 7, 6, 6, 11, 2].
Your goal is 68.
Your answer: 6 * 11 + 2
Your cards are [4, 10, 2, 5, 13, 5].
Your goal is 125.
Your answer: 5 * 5 * (10/2)
You will need at least Python 3.6.5 installed on your machine. Set up the environment and install dependencies.
# start in the repository directory
python3 -m venv venv
. venv/bin/activate
pip install -r requirements.txt
Then, you can play the game with:
python3 play_game.py
An Expression models a mathematical expression, like 5 + 2. There are
several different types of expressions. Most of the implementing
classes represent operations (e.g. addition, multiplication), and these
classes are built up recursively out of other Expressions. There is also
a Number implementing class that represents the base case in most of the
Expression methods. A number is pretty much a wrapper around an int.
The RandomExpressionGenerator takes a list of numbers and (randomly)
constructs an Expression from them. This is how the goal is computed
in each round of the game.
The Parser is used to parse input strings (e.g. "5+(12/4)") into
corresponding instances of our Expression classes. For example, it
might parse the string above into
Add(Number(5), Divide(Number(12), Number(3))).
The Deck keeps track of the cards left in the game, and is responsible
for picking cards from the deck, uniformly at random. In the context of
this game, a card is simply an integer between 1 and 13.
The CountdownGame keeps track of the game's state between rounds
and interacts with the player. It also aggregates all of the other
classes together and is in charge of the game's functionality.
I used Lark to create my Expression parser. Lark is fantastic—I just had to specify a grammar and a transformer, and it did all of the parsing work for me. I chose Lark because of its simplicity and documentation.
You can find it's documentation here, and an example here. To create the Expression, I drew heavily on a grammar that I put together for a project called deriv.
Tests were set up with the unittest python module. You can run them with:
# start in the repository directory
python3 -m unittest