Uiua

Decided to try and use Uiua for each day this year. At least I’m not the only one to get this idea ^^

Run with example input here

PartOne ← (
  &rs ∞ &fo "input-1.txt"
  ⊜(⊜⋕≠@ .)≠@\n.
  ≡⍆⍉
  ⌵/-
  /+
)

PartTwo ← (
  &rs ∞ &fo "input-1.txt"
  ⊜(⊜⋕≠@ .)≠@\n.
  ⊢⟜⊣⍉
  0
  ⍢(+⊙(:⊙(×⧻⊚◡⌕)↘1⟜⊢)|⋅(≠0⧻))
  ⊙(◌◌) # just cleaning up the stack
)

&p "Day 1:"
&pf "Part 1: "
&p PartOne
&pf "Part 2: "
&p PartTwo

Kotlin

No 💜 for Kotlin here?

import kotlin.math.abs

fun part1(input: String): Int {
    val diffs: MutableList<Int> = mutableListOf()
    val pair = parse(input)
    pair.first.sort()
    pair.second.sort()
    pair.first.forEachIndexed { idx, num ->
        diffs.add(abs(num - pair.second[idx]))
    }
    return diffs.sum()
}

fun part2(input: String): Int {
    val pair = parse(input)
    val frequencies = pair.second.groupingBy { it }.eachCount()
    var score = 0
    pair.first.forEach { num ->
        score += num * frequencies.getOrDefault(num, 0)
    }
    return score
}

private fun parse(input: String): Pair<MutableList<Int>, MutableList<Int>> {
    val left: MutableList<Int> = mutableListOf()
    val right: MutableList<Int> = mutableListOf()
    input.lines().forEach { line ->
        if (line.isNotBlank()) {
            val parts = line.split("\\s+".toRegex())
            left.add(parts[0].toInt())
            right.add(parts[1].toInt())
        }
    }
    return left to right
}