Skip to main content

Day 1: Calorie Counting

by @bishabosha

Puzzle description​

https://adventofcode.com/2022/day/1

Solution Summary​

First transform the input into a List of Inventory, each Inventory is a list of Int, representing the calorie count of an item in the inventory, this is handled in scanInventories.

Part 1​

Given the List of Inventory, we must first find the total calorie count of each inventory.

For a single Inventory, we do this using the sum method on its items property (found in the List class). e.g. inventory.items.sum.

Then use the map method on the List class, to transform each Inventory to its total calorie count with an anonymous function.

Then sort the resulting list of total calorie counts in descending order, this is provided by scala.math.Ordering.Int.reverse.

The maxInventories method handles the above, returning the top n total calorie counts.

For part 1, use maxInventories with n == 1 to create a singleton list of the largest calorie count.

Part 2​

As in part 1, construct the list of sorted total calorie counts with maxInventories. But instead, we need the first 3 elements. We then need to sum the resulting list.

Final Code​

import scala.math.Ordering

def part1(input: String): Int =
  maxInventories(scanInventories(input), 1).head

def part2(input: String): Int =
  maxInventories(scanInventories(input), 3).sum

case class Inventory(items: List[Int])

def scanInventories(input: String): List[Inventory] =
  val inventories = List.newBuilder[Inventory]
  var items = List.newBuilder[Int]
  for line <- input.linesIterator do
    if line.isEmpty then
      inventories += Inventory(items.result())
      items = List.newBuilder
    else items += line.toInt
  inventories.result()

def maxInventories(inventories: List[Inventory], n: Int): List[Int] =
  inventories
    .map(inventory => inventory.items.sum)
    .sorted(using Ordering.Int.reverse)
    .take(n)

Run it in the browser​

Part 1​

Part 2​

Solutions from the community​

Share your solution to the Scala community by editing this page.