Notebooks

Every problem ships a playground in jupytext percent format, plain Python in git and a notebook when you want one.

Every problem directory includes playground.py, a scratchpad for poking at inputs, inspecting data structures, and experimenting before you commit to an approach. See Problem Anatomy for where it fits.

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Percent format, not .ipynb

Playgrounds are stored as jupytext percent format: plain Python with # %% cell markers.

# %%
from helpers import assert_two_sum, run_two_sum
from solution import Solution

# %%
# Example test case
nums = [2, 7, 11, 15]
target = 9
expected = [0, 1]

# %%
result = run_two_sum(Solution, nums, target)
result

# %%
assert_two_sum(result, expected)

In git that means clean diffs, real code review, and mergeable history, with none of the JSON noise .ipynb would add.

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Open it as a notebook

Pick whichever fits your setup:

• VS Code: the Python extension supports # %% cells natively; open playground.py and run cells in the interactive window.
• JupyterLab with the jupytext contents manager: same experience, in the browser.
• One-off conversion: uv run jupytext --to ipynb leetcode/two_sum/playground.py gives you a real playground.ipynb.

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Convert back before committing

If you converted to .ipynb, convert back before you commit. The repo keeps only the .py form:

bake nb-to-py   # all .ipynb under leetcode/ -> py:percent, .ipynb deleted

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A scratchpad, not the contract

The playground imports the same helpers and solution as the tests, so what you probe here matches what the suite runs. Nothing in it is graded; test_solution.py stays the contract.