project-euler

projecteuler.net problems solutions.

We use Buck2 as the primary build system. The repo also contains generated Ninja files for lightweight smoke builds and Bazel metadata for targets that have BUILD files.

Freely distributed under MIT licence.

Recommendation for apps and libraries

New apps (binaries) and libraries should be buildable and runnable with all three supported build systems — Bazel, Buck2, and Ninja — so they work in every workflow (local dev, CI smoke builds, and Bazel-based tooling). Concretely, for each new directory:

1. Add a BUCK file describing the targets with cxx_library, cxx_binary, or cxx_test. Buck2 is the primary build system.
2. Add a BUILD file with the matching Bazel rules — cc_library, cc_binary, or cc_test (load them from @rules_cc//cc:defs.bzl). Keep the target names and dependency list in sync with the BUCK file.
3. Regenerate the Ninja metadata with python3 scripts/generate_ninja.py, which reads the BUCK (or BUILD) files and emits the per-directory build.ninja plus the root build.ninja. Commit the regenerated files.

Use workspace-root-relative includes (e.g. #include "bignum/bigint.h") so the same sources compile under every build system, and keep new CI smoke targets dependency-light. A minimal library + binary then builds and runs like this:

# Buck2 (primary)
buck2 build //path/to:target
buck2 run   //path/to:binary

# Bazel
bazel build //path/to:target
bazel run   //path/to:binary
# or: ./bBazel.sh //path/to:target

# Ninja (after regenerating with scripts/generate_ninja.py)
ninja path/to/binary
./build-ninja/bin/path/to/binary

Tests should be runnable as cc_test under Bazel (bazel test //path/to:...), as cxx_test / cxx_binary under Buck2, and as a Ninja binary target.

Building on Ubuntu Linux

The primary supported platform is Ubuntu Linux. To set up a fresh machine:

./setupUbuntu.sh

This installs the APT packages from ubuntuPackages.txt plus core build tools (including Ninja), the pip packages from ubuntuPipPackages.txt and pipPackages.txt, and the latest Buck2 release into ~/.local/bin.

Make sure ~/.local/bin is on your PATH, then build any project with:

./b.sh Normal           # builds //eulerNormal/... in opt mode
./r.sh Normal           # builds and runs //eulerNormal/...
./b.sh advent/2020/1    # builds //advent/2020/1/...
./bETFModelingBuck2.sh   # builds //ETFModeling:ETFModeling with Buck2
./bBazel.sh //advent/2024/1:all  # builds an existing Bazel target

The cCommon.sh helper uses buck2 from PATH, BUCK_BIN, or the standard ~/.local/bin/buck2 location used by setupUbuntu.sh. You can install only Buck2 with one of the platform installers:

./scripts/installBuck2Ubuntu.sh      # Ubuntu Linux
./scripts/installBuck2MacOS.sh       # macOS
powershell -ExecutionPolicy Bypass -File .\\scripts\\installBuck2Windows.ps1

You can also override the binary with BUCK_BIN=/path/to/buck2. Legacy Buck is retired for this repository.

Bazel is also available for the subset of the repository that has BUILD files. Use ./bBazel.sh <target> or call bazel build <target> directly. You can set BAZEL_BIN=/path/to/bazel to choose a specific Bazel/Bazelisk binary.

Building on macOS

The same b.sh / r.sh scripts work on macOS once buck2 is on PATH (e.g. brew install buck2). The Buck2 toolchain at toolchains/BUCK uses the system_cxx_toolchain from the bundled prelude, which picks up clang from PATH on macOS and g++/clang on Linux.

Continuous integration

The .github/workflows/ubuntu-buck2.yml and .github/workflows/ubuntu-ninja.yml workflows run on every push and PR. They install the Ubuntu dependency lists, download Buck2 where needed, and smoke-test the build on ubuntu-latest.