These are my solutions, written in Scala, using IntelliJ.
You can open this folder in IntelliJ and run each part individually from the IDE (open the file, right-click in the editor, select "Run [name]")
You can also run the code from the command line. Install sbt. From the top directory of this repo, build the project by running:
sbt assembly
To generate and display the solutions (including elapsed time):
# all the solutions
./target/universal/stage/bin/main
# just the solution for Day5Part1
./target/universal/stage/bin/main Day5Part1
# multiple solutions
./target/universal/stage/bin/main Day5Part1 Day5Part2