用地道 Kotlin 代码求解 Advent of Code 谜题

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:

Get ready for Advent of Code

We'll take you through the basic tips on how to get up and running with solving Advent of Code challenges with Kotlin:

  • Use this GitHub template to create projects
  • Check out the welcome video by Kotlin Developer Advocate, Sebastian Aigner:

YouTube 视频：Get Ready for Advent of Code 2021

Advent of Code 2022

Day 1: Calorie counting

Learn about the Kotlin Advent of Code template and convenience functions for working with strings and collections in Kotlin, such as maxOf() and sumOf(). See how extension functions can help you structure your solution in a nice manner.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 1 | Kotlin

Day 2: Rock paper scissors

Understand operations on the Char type in Kotlin, see how the Pair type and the to constructor work well with pattern matching. Understand how to order your own objects using the compareTo() function.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 2 | Kotlin

Day 3: Rucksack reorganization

Learn how the kotlinx.benchmark library helps you understand the performance characteristics of your code. See how set operations like intersect can help you select overlapping data, and see performance comparisons between different implementations of the same solution.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 3 | Kotlin

Day 4: Camp cleanup

See how infix and operator functions can make your code more expressive, and how extension functions for the String and IntRange types make it easy to parse input.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 4 | Kotlin

Day 5: Supply stacks

Learn about constructing more complex objects with factory functions, how to use regular expressions, and the double-ended ArrayDeque type.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 5 | Kotlin

Day 6: Tuning trouble

See more in-depth performance investigations with the kotlinx.benchmark library, comparing the characteristics of 16 different variations of the same solution.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 6 | Kotlin

Day 7: No space left on device

Learn how to model tree structures, and see a demo of generating Kotlin code programmatically.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 7 | Kotlin

Day 8: Treetop tree house

See the sequence builder in action, and how far a first draft of a program and an idiomatic Kotlin solution can differ (with special guest Roman Elizarov!).

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 8 | Kotlin

Day 9: Rope bridge

See the run function, labeled returns, and convenient standard library functions like coerceIn, or zipWithNext. See how you can construct lists of given sizes using the List and MutableList constructors, and get a peek at a Kotlin-based visualization of the problem statement.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 9 | Kotlin

Day 10: Cathode-ray tube

Learn how ranges and the in operator make checking ranges natural, how function parameters can be turned into receivers, and a brief exploration of the tailrec modifier.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 10 | Kotlin

Day 11: Monkey in the middle

See how you can move from mutable, imperative code to a more functional approach that makes use of immutable and read-only data structures. Learn about context receivers and how our guest built his own visualization library just for Advent of Code.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 11 | Kotlin

Day 12: Hill Climbing algorithm

Use queues, ArrayDeque, function references, and the tailrec modifier to solve path finding problems with Kotlin.

  • Read the puzzle description on Advent of Code
  • Check out the solution in the video:

YouTube Advent of Code 2022 Day 12 | Kotlin

Advent of Code 2021

Read our blog post about Advent of Code 2021

Day 1: Sonar sweep

Apply windowed and count functions to work with pairs and triplets of integers.

  • Read the puzzle description on Advent of Code
  • Check out the solution from Anton Arhipov on the Kotlin Blog or watch the video:

YouTube Advent of Code 2021 in Kotlin, Day 1: Sonar Sweep

Day 2: Dive!

Learn about destructuring declarations and the when expression.

  • Read the puzzle description on Advent of Code
  • Check out the solution from Pasha Finkelshteyn on GitHub or watch the video:

YouTube Advent of Code 2021 in Kotlin, Day 2: Dive!

Day 3: Binary diagnostic

Explore different ways to work with binary numbers.

  • Read the puzzle description on Advent of Code
  • Check out the solution from Sebastian Aigner on Kotlin Blog or watch the video:

YouTube Advent of Code 2021 in Kotlin, Day 3: Binary Diagnostic

Day 4: Giant squid

Learn how to parse the input and introduce some domain classes for more convenient processing.

  • Read the puzzle description on Advent of Code
  • Check out the solution from Anton Arhipov on the GitHub or watch the video:

YouTube Advent of Code 2021 in Kotlin, Day 4: Giant Squid

Advent of Code 2020

You can find all the solutions for the Advent of Code 2020 puzzles in our GitHub repository.

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:

YouTube Learn Kotlin With the Kotlin Team: Advent of Code 2020 #1

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:

YouTube Learn Kotlin with The Kotlin Team: Advent of Code 2020 #2

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:

YouTube Learn Kotlin with the Kotlin Team: Advent of Code 2020 #3

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:

YouTube Learn Kotlin with the Kotlin Team: Advent of Code 2020 #4

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:

YouTube Learn Kotlin with the Kotlin Team: Advent of Code 2020 #5

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:

YouTube Learn Kotlin with the Kotlin Team: Advent of Code 2020 #6

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:

YouTube Learn Kotlin with the Kotlin Team: Advent of Code 2020 #7

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:

YouTube Learn Kotlin with the Kotlin Team: Advent of Code 2020 #8

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:

YouTube Learn Kotlin with the Kotlin Team: Advent of Code 2020 #9

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