Problem file format

One JSON format imports problems everywhere: the problem library (Dashboard › Problems › Import), and the problem picker of the assignment, exam and contest forms (“Import problems”). A template to copy is served at /problem-template.json.

{
  "format": "gretlab-problems",
  "version": 1,
  "problems": [ { ...one problem... }, { ... } ]
}

A bare list of problems, or a single problem object, is accepted too. At most 100 problems per file and 8 MB per upload. Every problem is checked before any is saved: one mistake and nothing is imported, with the problem number, title and field named.

A problem

Field	Required	What it is
title	yes	Shown to students.
slug	no	The address (/problems/<slug>). Made from the title; a number is added if it’s taken.
level	no	easy (default), medium or hard.
statement	yes	The problem in Markdown: GitHub tables, lists, code blocks. Raw HTML is shown as text. Images: upload them in the editor after importing.
input, output, constraints	no	Input format, output format and constraints, shown under their own headings. A list of lines, or one string with a line each. Keep them out of the statement.
samples	yes, one or more	{ "input": "...", "output": "...", "points": 1 }. Shown to students as examples, and graded.
tests	no	Hidden tests, same shape. Students see only pass/fail and timing.
code	no	Per language (python, javascript, c, cpp, java): { "starter": "...", "solution": "..." }. The starter is exactly what a student’s editor opens with; the solution is shown under the editorial’s rules and is never sent to students otherwise.
hints	no	Up to 10, Markdown, revealed one at a time.
editorial	no	Markdown, unlocked by the practice rules.
tags	no	Up to 10 names.
timeLimitMs, memoryLimitMb	no	null for the defaults.
languages	no	Languages students may use, e.g. ["python", "cpp"]; null for all.

Outputs are compared the same way as in the editor: trailing spaces and the final newline don’t matter.

Where imported problems go

• Problem library import: choose whether they’re published, and whether they show in the library.
• From an assignment, exam or contest form: they’re ready for students but not in the library. Students reach them only through the work that uses them: an assignment once it opens, an exam once they start it, a contest once it starts. Use this for exams so nobody can practise the problems beforehand.