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Most puzzles in the Practice section are In/Out puzzles. You're given a problem, inputs to read in the stdin, and our system expects your program to print the requested answer in stdout, depending on the inputs.

An In/Out puzzle contains a statement, a default code, and test cases. It is also defined by tags and a difficulty from easy to very hard.

Test Cases and Validators

Most puzzles work with a system of test cases: visible IDE tests to help you verify your code solve the given problem, and corresponding hidden tests, called validators for the system to validate you solved the puzzle. More details about test cases

You solve these puzzles by passing all validators. Some puzzles (Code Golf, Optimization) will ask you to pass the tests and to optimize a specific criterion, and you'll be then ranked against other players based on that criterion.

You can have a look at the IDE test cases by clicking on the button at the top right of the test cases panel.

For each test, you can find on the left, the input data as it's sent to you in the stdin, and on the right, the expected output on stdout.

Clash of Code

Clash of Code puzzles are simple In/Out puzzles specially created for short multiplayer battles. They're aimed to be solvable in less than 15 minutes.

There are 3 possibles game modes in Clash of Code, assigned randomly:

  • Fastest: the most classic mode; the first player who passes all test cases wins.
  • Shortest: also known as "code golf"; the first player who passes all test cases with the least number of characters wins.
  • Reverse: same as fastest but the players need to guess what to do (the statement is hidden, only tests are shown); the first player who guesses what to do and passes all test cases wins.

There are no tags nor difficulty associated with a Clash of Code puzzle.

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