Collections

This post continues our “Idiomatic Kotlin” series and provides the solution for the Advent of Code Day 9* challenge. While solving it, we’ll look into different ways to manipulate lists in Kotlin. Day 9. Encoding error, part I We need to attack a weakness in data encrypted with the eXchange-Masking Addition System (XMAS)! The data is a list of numbers, and we need to find the first number in the list (starting from the 26th) that is not the sum of any 2 of the 25 numbers before it. We’ll call the number valid if it can be presented as a sum of two numbers from the previous sublist, a

Grouping and counting the characters in strings and collections is a very typical task given in coding interviews. Usually, the solutions for such tasks are quite simple. In this blog post, we learn about a few useful functions in Kotlin that make set operations really simple. The task: custom customs The task for the Advent of Code Day 6 challenge requires us to count the answers on customs declaration forms. We are provided with the results of the filled-in forms for different groups of people. Below is the original sample provided in the AoC Day 6 challenge: abc a b c ab ac