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H9A counts how many times a digit (0–9) appears across any range of numbers. Unlike brute-force scripts, it uses a closed-form O(log n) algorithm, so a range from 1 to 1,000,000,000,000 returns instantly. It prints a colorized, step-by-step breakdown of each decimal place, supports machine-readable JSON, and can render terminal-style screenshots.
H9A started as the classic puzzle "How many 9s are in 1–100?" (the answer is 20, and 99 counts twice). I turned it into a proper little Python package: a `h9a` CLI plus an importable library returning a per-place breakdown.
Highlights:
- O(log n) closed-form counting — no range iteration, so huge ranges are instant
- Step-by-step explanation of every decimal place (ones, tens, hundreds, ...)
- `--json` output for scripting, `--no-color` for terminals without ANSI
- `--screenshot` renders the output to a PNG with Pillow
- 74 tests, ruff + mypy + pre-commit, CI docs and container publishing
Install: `pip install h9a`
Docs: https://rkriad585.github.io/h9a/
Source: https://github.com/rkriad585/h9a
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About H9A on Product Hunt
“Count any digit in any range — instantly.”
H9A was submitted on Product Hunt and earned 2 upvotes and 1 comments, placing #134 on the daily leaderboard. H9A counts how many times a digit (0–9) appears across any range of numbers. Unlike brute-force scripts, it uses a closed-form O(log n) algorithm, so a range from 1 to 1,000,000,000,000 returns instantly. It prints a colorized, step-by-step breakdown of each decimal place, supports machine-readable JSON, and can render terminal-style screenshots.
H9A was featured in Open Source (68.7k followers), Developer Tools (517.6k followers) and GitHub (41.4k followers) on Product Hunt. Together, these topics include over 121.3k products, making this a competitive space to launch in.
Who hunted H9A?
H9A was hunted by RK Riad Khan. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
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RK Riad Khan