To start the backend:

• Install dependencies with mix deps.get
• Start the database with docker-compose up -d
• Create and migrate your database with mix ecto.setup
• Start Phoenix endpoint with mix phx.server

Now the server should be running on http://localhost:4000/

All of the endpoints are documented in Postman

As of now, users can create problems, define test cases, and execute arbitrary code written in C, Java, and Python3 against those test cases. A test case is defined as having a textual input, and an expected textual output. A solution must read its input from stdin, and write its output to a file whose name is given by the RESULT_FILE environment variable. Any stdout will be collected and returned to the user (for debugging and testing).

For example, one might create a problem isPalindrome of the form f: string -> boolean with a helpful description describing palindromes, then add some of the following test cases:

• "abc" => "false"
• "racecar" => "true"
• "abcba" => "true"
• "abccba" => "true"
• "abccb" => "false"
• "hello" => "false"

An example solution, written in python, might look like:

from os import environ
from sys import stderr

def main():
    filename = environ.get('RESULT_FILE')
    if filename is None:
        print("no RESULT_FILE environment variable", file=stderr)

    inputString = input()
    result = isPalindrome(inputString)
    result = repr(result).lower()

    with open(filename, 'w') as result_file:
        result_file.write(result)

def isPalindrome(string):
    return string == string[::-1]


main()

You'll notice however, that it would be ideal if everything other than the isPalindrome function could be generated from a description of the problem, allowing the student to skip the boilerplate (TODO).