[SPOILER ALERT] Advent of Code 2022: Day 1 Solutions

[Junilu Lacar]

SPOILER ALERT This thread contains solution code for Day 1 of Advent of Code 2022.






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SPOILER ALERT This thread contains solution code for Day 1 of Advent of Code 2022.

[Junilu Lacar]

Here's my Kotlin solution. My Main program already takes care of reading the input file and I have scaffolding that allows me to just call the solution, passing in a List<String> that it can then process according to the problem requirements.

From https://github.com/jlacar/adventofcode2022-kotlin/blob/main/untitled/src/main/kotlin/Day1.kt

fun day1Part1(input: List<String>) = calories(input, 1)

fun day1Part2(input: List<String>) = calories(input, 3)

private fun calories(input: List<String>, n: Int): Int {
    val cals: MutableList<Int> = mutableListOf()
    val maxCals: MutableList<Int> = mutableListOf()
    input.forEach { line ->
        if (line.isNotBlank()) {
            cals.add(line.toInt())
        } else {
            maxCals.add(cals.sumOf { it })
            cals.clear()
        }
    }
    maxCals.sortDescending()
    return maxCals.subList(0, n).sum()
}

Maybe there's a more idiomatic way to write this in Kotlin? Would love to see other solutions in other languages.

I should note that I "cheated" with the data files. I added a blank line at the end to trigger the total logic for the last group. Otherwise, I'd be off-by-one group or I'd have to add another statement like line 12 when the loop exits. Now that I think about it, I should probably do that anyway, for correctness.

[Junilu Lacar]

@Piet I was looking at your Day 1 solution on GitHub.

Regarding this:
       var sorted = elves.stream()            .mapToInt(e -> e.getSumOfCalories())            .boxed()            .sorted(Comparator.reverseOrder())            .toList()        ;        var resultA = sorted.stream().limit(1).mapToInt(i -> i).sum();        var resultB = sorted.stream().limit(3).mapToInt(i -> i).sum();
Do you need .boxed() on line 49? Doesn't mapToInt() already give you an IntStream?

[Liutauras Vilda]

Solutions for day01 are essentially the same. Probably that's idiomatic thinking of us developers than idiomatic language approach

(define input (map (λ (e) (string->number e)) (file->lines "input/day01.txt")))

(define (calories-calc calories sum calories-bag)
  (cond [(empty? calories) (sort (cons sum calories-bag) >)]
        [(not (car calories)) (calories-calc (cdr calories) 0 (cons sum calories-bag))]
        [else (calories-calc (cdr calories) (+ sum (car calories)) calories-bag)]))

(car (calories-calc input 0 '()))
(apply + (take (calories-calc input 0 '()) 3))

[Junilu Lacar]

Liu, this is the Racket solution, right? A little inscrutable for these Java/Kotlin eyes but it certainly is interesting, if only for its conciseness. Is cons on Line 5 like the Scala cons?

[Liutauras Vilda]

Junilu Lacar wrote:Liu, this is the Racket solution, right? A little inscrutable for these Java/Kotlin eyes but it certainly is interesting, if only for its conciseness. Is cons on Line 5 like the Scala cons?

Yes, it is Racket.  Indeed, it is significantly different. But you would find it fairly easy to grasp if you'd have touched Clojure to some good extent in the past. The latter is JVM language and undoubtedly much better known in industry. Those languages are similar in a way like Java and Kotlin are.

I saw on some social media (it was Twitter actually) where Uncle Bob (Robert C. Martin) in some past AoC years was solving those in Clojure.

I don't recall myself using cons in Scala in the past, and can't find documentation in intuitive way at the moment (no one can beat javadocs here), so don't want to mislead, but Racket's cons really makes a pair, or in that line 5 case, adds a number to an existing list, which in racket is a pair.

So it may sound weird that list '(1 2 3 4) is a pair, which you can access/slice it in any way you want. i.e.:
(car '(1 2 3 4)) => 1
(cdr '(1 2 3 4)) => '(2 3 4)

or

(first '(1 2 3 4)) => 1
(rest '(1 2 3 4)) => '(2 3 4)

more:
(cadr '(1 2 3 4)) => 2
(caddr '(1 2 3 4)) => 3
(cddr '(1 2 3 4)) => '(3 4)
(cdddr '(1 2 3 4)) => '(4)

And many other ways to achieve above, i.e. using take, drop.

No wonder why Lisp stands for List processing

[Piet Souris]

Junilu Lacar wrote:@Piet I was looking at your Day 1 solution on GitHub.

Regarding this:
       var sorted = elves.stream()            .mapToInt(e -> e.getSumOfCalories())            .boxed()            .sorted(Comparator.reverseOrder())            .toList()        ;        var resultA = sorted.stream().limit(1).mapToInt(i -> i).sum();        var resultB = sorted.stream().limit(3).mapToInt(i -> i).sum();
Do you need .boxed() on line 49? Doesn't mapToInt() already give you an IntStream?

An IntStream only has the sorted-method, without a Comparator. But now I wonder if when using just 'map' instead of 'mapToInt' will give me a List<Integer> straightaway. Gonna give it a try!

Just tried it:

var sorted = elves.stream()
    .map(e -> e.getSumOfCalories())
    .sorted(Comparator.reverseOrder())
    .toList()
;

works fine, even though getSumOfCalories() returns an int. Wonderful, that autoboxing!

[Junilu Lacar]

Liutauras Vilda wrote:I don't recall myself using cons in Scala in the past, and can't find documentation in intuitive way at the moment (no one can beat javadocs here), so don't want to mislead, but Racket's cons really makes a pair, or in that line 5 case, adds a number to an existing list, which in racket is a pair.

So it may sound weird that list '(1 2 3 4) is a pair, which you can access/slice it in any way you want. i.e.:

Yeah, it's like the Scala cons - it's used for list processing.