Advent of Code 2021

Coverage Status Go Report Card License

Solutions for the 2021 Advent of Code


This project makes use of Go 1.17.

go mod download
go test ./...

Running the Solutions

To run a solution, use the problem name followed by the path to an input file.

For example, to run problem 2a:

$ go run ./main.go 2a ./day2/input.txt
Answer: 9633
Took 999.4µs

Adding New Solutions

A generator program is included that makes templates for each day, automatically
downloading challenge input and updating the root command to add new subcommands
for each problem. Running go generate from the repo root will generate the
following for each day that is currently accessible:

  • challenge/day<N>/import.go: A “glue” file combining commands for both of the day’s problems to simplify wiring up subcommands
  • challenge/day<N>/a.go: The main problem implementation, containing a cobra command A and the implementation func a(*challenge.Input) int
  • challenge/day<N>/a_test.go: A basic test template
  • challenge/day<N>/input.txt: The challenge input

Additionally, challenge/cmd/cmd.go will be regenerated to import and add all

This requires goimports be available on your $PATH. Additionally, you must be
logged into in Chrome so the generator can use your session
cookie to download challenge input.

Existing solutions and challenge inputs will be skipped instead of regenerated.


These solutions are licensed under the MIT License.

See LICENSE for details.


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