Crate gcj_helper

A helper library for Google Code Jam solutions.

In the Google Code Jam, solving a problem typically requires the following steps:

1. Open an input file containing a series of test cases.
2. Open an output file where solutions will be written.
3. Read the first line from the input file, which consists solely of an unsigned integer specifying the number of test cases in the input file.
4. For each test case, perform the following steps:
   1. Obtain the corresponding test data by reading one or more lines from the input file (it may be a fixed number, or specified within the test data itself).
   2. Perform some logic using the test data, in order to obtain a set of results.
   3. Write the string "Case #N:" (where N is the number of completed test cases) followed by the results obtained in the previous step, formatted as the problem requires.

Writing code to handle all of the above is tedious and time-consuming, in a situation where every microsecond counts. gcj-helper is designed to handle the boilerplate, so you can focus on writing solutions instead.

The TestEngine type

To execute test cases, you need to create a TestEngine and call TestEngine::run(). TestEngine::run() accepts two closures:

1. A parser that reads from an input file and returns the data for one test case.
2. A solver that performs logic on the data for one test case and returns a result, encoded as a Display type.

This two-step process to writing solutions is useful for two reasons:

• It seperates parsing from the solution itself, making your code easier to read;
• It enables test case parallelisation if the parallel feature is enabled, improving run-time performance at the cost of increased build times.

The InputReader type

gcj-helper provides parsers with access to an InputReader, a simple wrapper around a std::fs::File. InputReader implements io::BufRead and also provides a convenience method, read_next_line(), which reads a line of text from an input file and truncates the end-of-line marker if one is present.

Formatting test results

Before each test case, the TestEngine writes the string "Case #N:", where N is the current test case. This does not prepend or append any whitespace. This means that if the colon must be followed by a space, your result should begin with one, and that the result must end with a newline.

Structs

InputReader	Supports reading from an input file.
TestEngine	Facilitates the execution of problem solving code.