problem-solving

Collection of leetcode & codeforces problems solved using Java 8, Java 17, Kotlin and Python, plus small Python projects (python/projects/)

JVM solutions use the leetcode-editor IntelliJ plugin. Python solutions use the leetgo CLI (see LeetCode with leetgo).

IDE setup

Open the repo root in IntelliJ IDEA. It's a plain IntelliJ (JPS) project: the modules are listed in .idea/modules.xml, with one .iml per language module. There's no Gradle or Bazel.

Module	Language level	Notes
leetcode-java8, codeforces-java8	Java 8	JUnit 5 for codeforces-java8 tests
leetcode-java17, codeforces-java17	Java 17
leetcode-kotlin	Kotlin (JVM 17)	KotlinJavaRuntime library
python (python/python.iml)	Python 3.14	everything under python/

The project JDK is zulu-17. The JUnit and Kotlin libraries are Maven-backed (.idea/libraries/), and IntelliJ downloads them on first open.

To run a solution, use the gutter arrow on main. New files need no build edits.

Python

All Python lives in python/, a uv project on Python 3.14. python/pyproject.toml holds the dev dependencies (pytest, plus leetgo_py and sortedcontainers for leetgo solutions) and the pytest config. uv.lock pins them. Run uv commands from python/:

cd python
uv sync          # create/refresh python/.venv
uv run pytest    # run every Python test
uv run python projects/01_calc/calc.py

In IntelliJ, set the python module's interpreter to the uv python/.venv: Settings → Project Structure → Modules → python, or Add Interpreter → uv → existing environment. Then a right-click → Run on any .py file gives you a normal interactive process, and pytest is the test runner.

Layout

python/
  pyproject.toml  uv.lock  .python-version  python.iml  leetgo.yaml
  tools/       pytest_leetgo plugin
  projects/    the project track (copy 00_template/)
  leetcode/    leetgo problems

Each top-level directory under projects/ or leetcode/ is one problem or project. Modules in a directory import each other flatly (from greet import greet), because both pytest and the script runner put the file's own directory on sys.path. Keep test file names unique across directories (test_<project>.py).

Adding dependencies

uv add --dev <package>

LeetCode with leetgo

Install: go install github.com/j178/leetgo@v1.5.0 (and put $(go env GOPATH)/bin on PATH). Log in to leetcode.com in your browser; leetgo reads the session cookies from it (python/leetgo.yaml → leetcode.credentials).

cd python
leetgo pick 150            # leetcode/0150.evaluate-reverse-polish-notation/
                           #   solution.py, testcases.txt (examples), question.md
uv run pytest leetcode/0150.evaluate-reverse-polish-notation
leetgo submit last

• Write the solution between # @lc code=begin and # @lc code=end. Only that part is submitted; the if __name__ == "__main__": harness below it is for local runs.
• testcases.txt holds the examples. Add your own cases in the same input: / output: format. A case without an output is skipped locally.
• Each example becomes a pytest item (case1, case2, ...) via python/tools/pytest_leetgo.py, so they show up individually in IntelliJ's test runner.
• The extra submission item reruns all examples using only the code inside the markers, plus from typing import *, ListNode and TreeNode. It fails if you rely on imports or helpers defined outside the markers. Put imports (collections, heapq, ...) inside the markers.
• Outputs are compared as JSON (floats within 1e-5). Top-level lists ignore order when the question says "in any order". For anything else (nested lists in any order, multiple valid answers), add a judge.py next to solution.py:

  def judge(expected, actual) -> bool:
      return sorted(map(sorted, expected)) == sorted(map(sorted, actual))

• leetgo test last -L also works; it uses its own venv in python/leetcode/.venv and doesn't know about judge.py.