2026年7月17日

A 1280x900 cover image for an article about how Sudoku generators work and why difficulty settings matter.

Sudoku Generator: Why a Fresh Puzzle Every Morning Is Harder Than It Looks

By xiezixing 2026年7月17日

A Sudoku generator has three hidden jobs — and the difference between a chore and a craft comes down to whether the difficulty label is honest. Here is how to read the puzzle the tool hands you.

Article cover poster for Words to Number text-processing tool article

When Your Auditor Writes Numbers in English

By xiezixing 2026年7月17日

Number words are the kind of data no one notices until they break the pipeline.…

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The R-Squared Trap: Why Your Best-Fit Line Can Quietly Lie to You

By xiezixing 2026年7月17日

A high R-squared feels like a verdict. The number comes back at 0.92, the slope…

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IBAN & SWIFT Validator: four checks, one verifier

By xiezixing 2026年7月17日

Cross-border payments need a four-step validator: strip whitespace, check length against country, run mod-97 for IBANs, and verify the 8 or 11 character SWIFT/BIC structure. Here is the exact recipe and the five traps that break it in production.

TOTP and HOTP offline generator guide: RFC 6238, RFC 4226, HMAC options, and time windows

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The QR Code Is Not the Whole 2FA Setup

By xiezixing 2026年7月17日

A practical guide to comparing TOTP and HOTP codes by making the shared secret, HMAC algorithm, counter, digits, and time window explicit.

Before You Delete an Outlier - six question data cleaning protocol

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Before You Delete an Outlier: A 6-Question Data Cleaning Protocol

By xiezixing 2026年7月17日

A practical protocol for detecting, marking, and processing extreme values without deleting useful evidence.