Beginner to Advanced Code Library

Build a Kotlin function that takes a raw phone number string and converts it into a clean, standardized E.164-style format. You’ll handle common punctuation, validate the digits, and return either a formatted result or a clear error message.

Learn how to calculate the sum of digits in Kotlin with this beginner-friendly example. This step-by-step snippet demonstrates input validation, safe integer parsing, and a clean functional approach using map and sum—perfect for mastering basic number algorithms in Kotlin.

Learn how to print classic star and number patterns in Kotlin, including solid squares, hollow squares, triangles, pyramids, and number triangles. This beginner-friendly example demonstrates loops, input validation, and clean string-building techniques.