Kotlin Help

Advent of Code puzzles in idiomatic Kotlin

Advent of Code is an annual December event, where holiday-themed puzzles are published every day from December 1 to December 25. With the permission of Eric Wastl, creator of Advent of Code, we'll show how to solve these puzzles using the idiomatic Kotlin style.

Day 1: Report repair

Explore input handling, iterating over a list, different ways of building a map, and using the let function to simplify your code.

  • Read the puzzle description on Advent of Code

  • Check out the solution from Svetlana Isakova on the Kotlin Blog or watch the video:

Day 2: Password philosophy

Explore string utility functions, regular expressions, operations on collections, and how the let function can be helpful to transform your expressions.

  • Read the puzzle description on Advent of Code

  • Check out the solution from Svetlana Isakova on the Kotlin Blog or watch the video:

Day 3: Toboggan trajectory

Compare imperative and more functional code styles, work with pairs and the reduce() function, edit code in the column selection mode, and fix integer overflows.

  • Read the puzzle description on Advent of Code

  • Check out the solution from Mikhail Dvorkin on GitHub or watch the video:

Day 4: Passport processing

Apply the when expression and explore different ways of how to validate the input: utility functions, working with ranges, checking set membership, and matching a particular regular expression.

  • Read the puzzle description on Advent of Code

  • Check out the solution from Sebastian Aigner on the Kotlin Blog or watch the video:

Day 5: Binary boarding

Use the Kotlin standard library functions (replace(), toInt(), find()) to work with the binary representation of numbers, explore powerful local functions, and learn how to use the max() function in Kotlin 1.5.

  • Read the puzzle description on Advent of Code

  • Check out the solution from Svetlana Isakova on the Kotlin Blog or watch the video:

Day 6: Custom customs

Learn how to group and count characters in strings and collections using the standard library functions: map(), reduce(), sumOf(), intersect(), and union().

  • Read the puzzle description on Advent of Code

  • Check out the solution from Anton Arhipov on the Kotlin Blog or watch the video:

Day 7: Handy haversacks

Learn how to use regular expressions, use Java's compute() method for HashMaps from Kotlin for dynamic calculations of the value in the map, use the forEachLine() function to read files, and compare two types of search algorithms: depth-first and breadth-first.

  • Read the puzzle description on Advent of Code

  • Check out the solution from Pasha Finkelshteyn on the Kotlin Blog or watch the video:

Day 8: Handheld halting

Apply sealed classes and lambdas to represent instructions, apply Kotlin sets to discover loops in the program execution, use sequences and the sequence { } builder function to construct a lazy collection, and try the experimental measureTimedValue() function to check performance metrics.

  • Read the puzzle description on Advent of Code

  • Check out the solution from Sebastian Aigner on the Kotlin Blog or watch the video:

Day 9: Encoding error

Explore different ways to manipulate lists in Kotlin using the any(), firstOrNull(), firstNotNullOfOrNull(), windowed(), takeIf(), and scan() functions, which exemplify an idiomatic Kotlin style.

  • Read the puzzle description on Advent of Code

  • Check out the solution from Svetlana Isakova on the Kotlin Blog or watch the video:

What’s next?

Last modified: 30 April 2022