Uiua

This turned out to be reasonably easy in Uiua, though this solution relies on macros which maybe slow it down.

(edit: removing one macro sped it up quite a bit)

(edit2: Letting Uiua build up an n-dimensional array turned out to be the solution, though sadly my mind only works in 3 dimensions. Now runs against the live data in around 0.3 seconds.)

Try it here

Data   ← ⊜(□⊜⋕⊸(¬∈": "))⊸≠@\n "190: 10 19\n3267: 81 40 27\n83: 17 5\n156: 15 6\n7290: 6 8 6 15\n161011: 16 10 13\n192: 17 8 14\n21037: 9 7 18 13\n292: 11 6 16 20"
Calib! ← ≡◇⊢▽⊸≡◇(∈♭/[^0]:°⊂) # Calibration targets which can be constructed from their values.
&p/+Calib!⊃(+|×)Data
&p/+Calib!⊃(+|×|+×ⁿ:10+1⌊ₙ₁₀,)Data

Python

It is a tree search

def parse_input(path):

  with path.open("r") as fp:
    lines = fp.read().splitlines()

  roots = [int(line.split(':')[0]) for line in lines]
  node_lists = [[int(x)  for x in line.split(':')[1][1:].split(' ')] for line in lines]

  return roots, node_lists

def construct_tree(root, nodes, include_concat):

  levels = [[] for _ in range(len(nodes)+1)]
  levels[0] = [(str(root), "")]
  # level nodes are tuples of the form (val, operation) where both are str
  # val can be numerical or empty string
  # operation can be *, +, || or empty string

  for indl, level in enumerate(levels[1:], start=1):

    node = nodes[indl-1]

    for elem in levels[indl-1]:

      if elem[0]=='':
        continue

      if elem[0][-len(str(node)):] == str(node) and include_concat:
        levels[indl].append((elem[0][:-len(str(node))], "||"))
      if (a:=int(elem[0]))%(b:=int(node))==0:
        levels[indl].append((str(int(a/b)), '*'))
      if (a:=int(elem[0])) - (b:=int(node))>0:
        levels[indl].append((str(a - b), "+"))

  return levels[-1]

def solve_problem(file_name, include_concat):

  roots, node_lists = parse_input(Path(cwd, file_name))
  valid_roots = []

  for root, nodes in zip(roots, node_lists):

    top = construct_tree(root, nodes[::-1], include_concat)

    if any((x[0]=='1' and x[1]=='*') or (x[0]=='0' and x[1]=='+') or
           (x[0]=='' and x[1]=='||') for x in top):

      valid_roots.append(root)

  return sum(valid_roots)

Haskell

import Control.Arrow
import Data.Char
import Text.ParserCombinators.ReadP

numP = read <$> munch1 isDigit
parse = endBy ((,) <$> (numP <* string ": ") <*> sepBy numP (char ' ')) (char '\n')

valid n [m] = m == n
valid n (x : xs) = n > 0 && valid (n - x) xs || (n `mod` x) == 0 && valid (n `div` x) xs

part1 = sum . fmap fst . filter (uncurry valid . second reverse)

concatNum r = (+r) . (* 10 ^ digits r)
    where
        digits = succ . floor . logBase 10 . fromIntegral

allPossible [n] = [n]
allPossible (x:xs) = ((x+) <$> rest) ++ ((x*) <$> rest) ++ (concatNum x <$> rest)
    where
        rest = allPossible xs

part2 = sum . fmap fst . filter (uncurry elem . second (allPossible . reverse))

main = getContents >>= print . (part1 &&& part2) . fst . last . readP_to_S parse

C

Big integers and overflow checking, what else is there to say 😅​

::: spoiler Code

#include "common.h"

/* returns 1 on sucess, 0 on overflow */
static int
concat(uint64_t a, uint64_t b, uint64_t *out)
{
	uint64_t mul;

	for (mul=1; mul<=b; mul*=10) ;

	return 
	    !__builtin_mul_overflow( mul, a, out) &&
	    !__builtin_add_overflow(*out, b, out);
}

static int
recur(uint64_t expect, uint64_t acc, uint64_t arr[], int n, int p2)
{
	uint64_t imm;

	return
	    n < 1 ? acc == expect :
	    acc >= expect ? 0 :
	    recur(expect, acc + arr[0], arr+1, n-1, p2) ||
	    recur(expect, acc * arr[0], arr+1, n-1, p2) ||
	    (p2 && concat(acc, arr[0], &imm)
	        && recur(expect, imm, arr+1, n-1, p2));
}

int
main(int argc, char **argv)
{
	char buf[128], *tok, *rest;
	uint64_t p1=0, p2=0, arr[32], expect;
	int n;

	if (argc > 1)
		DISCARD(freopen(argv[1], "r", stdin));
	
	while ((rest = fgets(buf, sizeof(buf), stdin))) {
		assert(strchr(buf, '\n'));
		expect = atoll(strsep(&rest, ":"));

		for (n=0; (tok = strsep(&rest, " ")); n++) {
			assert(n < (int)LEN(arr));
			arr[n] = atoll(tok);
		}

		p1 += recur(expect, 0, arr, n, 0) * expect;
		p2 += recur(expect, 0, arr, n, 1) * expect;
	}

	printf("07: %"PRIu64" %"PRIu64"\n", p1, p2);
	return 0;
}

:::

https://github.com/sjmulder/aoc/blob/master/2024/c/day07.c

Uiua

Credits to @[email protected] for the approach of using reduce and also how to split the input by multiple characters.
I can happily say that I learned quite a bit today, even though the first part made me frustrated enough that I went searching for other approaches ^^

Part two just needed a simple modification. Changing how the input is parsed and passed to the adapted function took longer than changing the function itself actually.

Run with example input here

PartOne ← (
  &rs ∞ &fo "input-7.txt"
  ⊜□≠@\n.
  ≡◇(⊜□≠@:.)
  ≡⍜⊡⋕0
  ≡⍜(°□⊡1)(⊜⋕≠@ .)
  ⟜(⊡0⍉)

  # own attempt, produces a too low number
  # ≡(:∩°□°⊟
  #   ⍣(⍤.◡⍣(1⍤.(≤/×)⍤.(≥/+),,)0
  #     ⊙¤⋯⇡ⁿ:2-1⊸⧻
  #     ⊞(⍥(⟜⍜(⊙(↙2))(⨬+×⊙°⊟⊡0)
  #         ↘1
  #       )⧻.
  #       ⍤.=0⧻.
  #     )
  #     ∈♭◌
  #   )0)

  # reduce approach found on the programming.dev AoC community by [email protected]
  ≡(◇(∈/(◴♭[⊃(+|×)]))⊡0:°⊂)
  °□/+▽
)

PartTwo ← (
  &rs ∞ &fo "input-7.txt"
  ⊜(□⊜⋕¬∈": ".)≠@\n.
  ⟜≡◇⊢
  ≡◇(∈/(◴♭[≡⊃⊃(+|×|⋕$"__")]):°⊂)
  °□/+▽
)

&p "Day 7:"
&pf "Part 1: "
&p PartOne
&pf "Part 2: "
&p PartTwo

Haskell

I'm not very proud, I copied my code for part two.

import Control.Arrow hiding (first, second)

import qualified Data.List as List
import qualified Data.Char as Char

parseLine l = (n, os)
        where
                n = read . takeWhile (Char.isDigit) $ l
                os = map read . drop 1 . words $ l

parse :: String -> [(Int, [Int])]
parse s = map parseLine . takeWhile (/= "") . lines $ s

insertOperators target (r:rs) = any (target ==) (insertOperators' r rs)
insertOperators' :: Int -> [Int] -> [Int]
insertOperators' acc []     = [acc]
insertOperators' acc (r:rs) = insertOperators' (acc+r) rs ++ insertOperators' (acc*r) rs

insertOperators2 target (r:rs) = any (target ==) (insertOperators2' r rs)
insertOperators2' :: Int -> [Int] -> [Int]
insertOperators2' acc []     = [acc]
insertOperators2' acc (r:rs) = insertOperators2' (acc+r) rs ++ insertOperators2' (acc*r) rs ++ insertOperators2' concatN rs
        where
                concatN = read (show acc ++ show r)

part1 ls = filter (uncurry insertOperators)
        >>> map fst
        >>> sum
        $ ls
part2 ls = filter (uncurry insertOperators2)
        >>> map fst
        >>> sum
        $ ls

main = getContents >>= print . (part1 &&& part2) . parse

Haskell

A surprisingly gentle one for the weekend! Avoiding string operations for concatenate got the runtime down below one second on my machine.

import Control.Arrow
import Control.Monad
import Data.List
import Data.Maybe

readInput :: String -> [(Int, [Int])]
readInput = lines >>> map (break (== ':') >>> (read *** map read . words . tail))

equatable :: [Int -> Int -> Int] -> (Int, [Int]) -> Bool
equatable ops (x, y : ys) = elem x $ foldM apply y ys
  where
    apply a y = (\op -> a `op` y) <$> ops

concatenate :: Int -> Int -> Int
concatenate x y = x * mag y + y
  where
    mag z = fromJust $ find (> z) $ iterate (* 10) 10

main = do
  input <- readInput <$> readFile "input07"
  mapM_
    (print . sum . map fst . (`filter` input) . equatable)
    [ [(+), (*)],
      [(+), (*), concatenate]
    ]

Python

Takes ~5.3s on my machine to get both outputs. Not sure how to optimize it any further other than running the math in threads? Took me longer than it should have to realize a lot of unnecessary math could be cut if the running total becomes greater than the target while doing the math. Also very happy to see that none of the inputs caused the recursive function to hit Python's max stack depth.

::: spoiler Code

import argparse
import os


class Calibrations:
    def __init__(self, target, operators) -> None:
        self.operators = operators
        self.target = target
        self.target_found = False

    def do_math(self, numbers, operation) -> int:
        if operation == "+":
            return numbers[0] + numbers[1]
        elif operation == "*":
            return numbers[0] * numbers[1]
        elif operation == "||":
            return int(str(numbers[0]) + str(numbers[1]))

    def all_options(self, numbers, last) -> int:
        if len(numbers) < 1:
            return last
        for j in self.operators:
            # If we found our target already, abort
            # If the last value is greater than the target, abort
            if self.target_found or last > self.target:
                return
            total = self.all_options(
                numbers[1:], self.do_math((last, numbers[0]), j)
            )
            if total == self.target:
                self.target_found = True

    def process_line(self, line) -> int:
        numbers = [int(x) for x in line.split(":")[1].strip().split()]
        self.all_options(numbers[1:], numbers[0])
        if self.target_found:
            return self.target
        return 0


def main() -> None:
    path = os.path.dirname(os.path.abspath(__file__))
    parser = argparse.ArgumentParser(description="Bridge Repair")
    parser.add_argument("filename", help="Path to the input file")
    args = parser.parse_args()
    sum_of_valid = [0, 0]
    with open(f"{path}/{args.filename}", "r") as f:
        for line in f:
            line = line.strip()
            target = int(line.split(":")[0])
            for idx, ops in enumerate([["+", "*"], ["+", "*", "||"]]):
                c = Calibrations(target, ops)
                found = c.process_line(line)
                sum_of_valid[idx] += found
                if found:
                    break
    for i in range(0, 2):
        part = i + 1
        print(
            "The sum of valid calibrations for Part "
            + f"{part} is {sum(sum_of_valid[:part])}"
        )


if __name__ == "__main__":
    main()

:::

https://github.com/stevenviola/advent-of-code-2024

Nim

Bruteforce, my beloved.

Wasted too much time on part 2 trying to make combinations iterator (it was very slow). In the end solved both parts with 3^n and toTernary.

Runtime: 1.5s

func digits(n: int): int =
  result = 1; var n = n
  while (n = n div 10; n) > 0: inc result

func concat(a: var int, b: int) =
  a = a * (10 ^ b.digits) + b

func toTernary(n: int, len: int): seq[int] =
  result = newSeq[int](len)
  if n == 0: return
  var n = n
  for i in 0..<len:
    result[i] = n mod 3
    n = n div 3

proc solve(input: string): AOCSolution[int, int] =
  for line in input.splitLines():
    let parts = line.split({':',' '})
    let res = parts[0].parseInt
    var values: seq[int]
    for i in 2..parts.high:
      values.add parts[i].parseInt

    let opsCount = values.len - 1
    var solvable = (p1: false, p2: false)
    for s in 0 ..< 3^opsCount:
      var sum = values[0]
      let ternary = s.toTernary(opsCount)
      for i, c in ternary:
        case c
        of 0: sum *= values[i+1]
        of 1: sum += values[i+1]
        of 2: sum.concat values[i+1]
        else: raiseAssert"!!"
      if sum == res:
        if ternary.count(2) == 0:
          solvable.p1 = true
        solvable.p2 = true
        if solvable == (true, true): break
    if solvable.p1: result.part1 += res
    if solvable.p2: result.part2 += res

---

Codeberg repo

Java

Today was pretty easy one but for some reason I spent like 20 minutes overthinking part 2 when all it needed was one new else if. I initially through the concatenation operator would take precedence even tho it clearly says "All operators are still evaluated left-to-right" in the instructions..

I'm sure there are optimizations to do but using parallelStreams it only takes around 300ms total on my machine so there's no point really

::: spoiler The code

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Arrays;
import java.util.List;

public class Day7 {
    public static void main(final String[] _args) throws IOException {
        final List<Equation> equations = Files.readAllLines(Path.of("2024\\07\\input.txt"), StandardCharsets.UTF_8).stream()
            .map(line -> line.split(":\\s"))
            .map(line -> new Equation(
                    Long.parseLong(line[0]),
                    Arrays.stream(line[1].split("\\s"))
                        .map(Integer::parseInt)
                        .toArray(Integer[]::new)
                )
            ).toList();

        final char[] part1Operators = {'+', '*'};
        System.out.println("Part 1: " + equations.parallelStream()
            .mapToLong(equation -> getResultIfPossible(equation, part1Operators))
            .sum()
        );

        final char[] part2Operators = {'+', '*', '|'};
        System.out.println("Part 2: " + equations.parallelStream()
            .mapToLong(equation -> getResultIfPossible(equation, part2Operators))
            .sum()
        );
    }

    private static Long getResultIfPossible(final Equation equation, final char[] operators) {
        final var permutations = Math.pow(operators.length, equation.values.length - 1);
        for (int i = 0; i < permutations; i++) {
            long result = equation.values[0];
            int count = i;

            for (int j = 0; j < equation.values.length - 1; j++) {
                // If the result is already larger than the expected one, we can short circuit here to save some time
                if (result > equation.result) {
                    break;
                }

                final char operator = operators[count % operators.length];
                count /= operators.length;

                if (operator == '+') { result += equation.values[j + 1]; }
                else if (operator == '*') { result *= equation.values[j + 1]; }
                else if (operator == '|') { result = Long.parseLong(String.valueOf(result) + String.valueOf(equation.values[j + 1])); }
                else {
                    throw new RuntimeException("Unsupported operator " + operator);
                }
            }

            if (result == equation.result) {
                return result;
            }
        }

        return 0L;
    }

    private static record Equation(long result, Integer[] values) {}
}

:::

Dart

Suspiciously easy, so let's see how tomorrow goes.... (edit: forgot to put the language! Dart for now, thinking about Uiua later)

import 'package:more/more.dart';

var ops = [(a, b) => a + b, (a, b) => a * b, (a, b) => int.parse('$a$b')];

bool canMake(int target, List<int> ns, int sofar, dynamic ops) {
  if (ns.isEmpty) return target == sofar;
  for (var op in ops) {
    if (canMake(target, ns.sublist(1), op(sofar, ns.first), ops)) return true;
  }
  return false;
}

solve(List<String> lines, dynamic ops) {
  var sum = 0;
  for (var line in lines.map((e) => e.split(' '))) {
    var target = int.parse(line.first.skipLast(1));
    var ns = line.skip(1).map(int.parse).toList();
    sum += (canMake(target, ns.sublist(1), ns.first, ops)) ? target : 0;
  }
  return sum;
}

part1(List<String> lines) => solve(lines, ops.sublist(0, 2));
part2(List<String> lines) => solve(lines, ops);

Factor

::: spoiler spoiler

TUPLE: equation value numbers ;
C: <equation> equation

: get-input ( -- equations )
  "vocab:aoc-2024/07/input.txt" utf8 file-lines [
    split-words unclip but-last string>number
    swap [ string>number ] map <equation>
  ] map ;

: possible-quotations ( funcs numbers -- quots )
  dup length 1 -
  swapd all-selections
  [ unclip swap ] dip
  [ zip concat ] with map
  swap '[ _ prefix >quotation ] map ;

: possibly-true? ( funcs equation -- ? )
  [ numbers>> possible-quotations ] [ value>> ] bi
  '[ call( -- n ) _ = ] any? ;

: solve ( funcs -- n )
  get-input
  [ possibly-true? ] with filter
  [ value>> ] map-sum ;

: part1 ( -- n )
  { + * } solve ;

: _|| ( m n -- mn )
  [ number>string ] bi@ append string>number ;

: part2 ( -- n )
  { + * _|| } solve ;

:::

Lisp

Could probably go much faster if I kept track of calculations to not repeat, but 4 seconds for part 2 on my old laptop is good enough for me. Also, not really a big change from part 1 to part 2.

::: spoiler Part 1 and 2

(defstruct calibration result inputs)

(defun p1-process-line (line)
  (let ((parts (str:words line)))
    (make-calibration :result (parse-integer (car parts) :junk-allowed t)
                      :inputs (mapcar #'parse-integer (cdr parts)))))

(defun apply-opperators (c opps)
  (let ((accum (car (calibration-inputs c))))
  (loop for o in opps
        for v in (cdr (calibration-inputs c))
        until (> accum (calibration-result c))
        if (eql o 'ADD)
          do (setf accum (+ accum v))
        else if (eql o 'MUL)
          do (setf accum (* accum v))
        else
          do (setf accum (+ v (* accum (expt 10 (1+ (floor (log v 10)))))))
        finally (return accum)
        )))

(defun generate-operators (item-count)
  (labels ((g-rec (c results)
             (if (< c 1)
                 results
                 (g-rec (1- c) (loop for r in results
                                     collect (cons 'ADD r)
                                     collect (cons 'MUL r))))))
    (g-rec (1- item-count) '((ADD) (MUL)))))

(defun generate-ops-hash (c gen-ops)
  (let ((h (make-hash-table)))
    (dotimes (x c)
      (setf (gethash (+ 2 x) h) (funcall gen-ops (+ 1 x))))
    h))

(defun validate-calibration (c ops-h)
  (let ((r (calibration-result c))
        (ops (gethash (length (calibration-inputs c)) ops-h)))
    (loop for o in ops
          for v = (apply-opperators c o)
          when (= v r)
            return t)))

(defun run-p1 (file) 
  (let ((calibrations  (read-file file #'p1-process-line))
        (ops (generate-ops-hash 13 #'generate-operators)))
    (loop for c in calibrations
          when (validate-calibration c ops)
            sum (calibration-result c))))

(defun generate-operators-p2 (item-count)
  (labels ((g-rec (c results)
             (if (< c 1)
                 results
                 (g-rec (1- c) (loop for r in results
                                     collect (cons 'ADD r)
                                     collect (cons 'MUL r)
                                     collect (cons 'CAT r))))))
    (g-rec (1- item-count) '((ADD) (MUL) (CAT)))))

(defun run-p2 (file) 
  (let ((calibrations  (read-file file #'p1-process-line))
        (ops (generate-ops-hash 13 #'generate-operators-p2)))
    (loop for c in calibrations
          when (validate-calibration c ops)
            sum (calibration-result c))))

:::

python

45s on my machine for first shot, trying to break my will to brute force 😅. I'll try improving on it in a bit after I smoke another bowl and grab another drink.

::: spoiler solution

import itertools
import re
import aoc

def ltr(e):
    r = int(e[0])
    for i in range(1, len(e), 2):
        o = e[i]
        n = int(e[i + 1])
        if o == '+':
            r += n
        elif o == '*':
            r *= n
        elif o == '||':
            r = int(f"{r}{n}")
    return r

def pl(l, os):
    d = [int(x) for x in re.findall(r'\d+', l)]
    t, ns = d[0], d[1:]
    ops = list(itertools.product(os, repeat=len(ns) - 1))
    for o in ops:
        e = str(ns[0])
        for i, op in enumerate(o):
            e += f" {op} {ns[i + 1]}"
        r = ltr(e.split())
        if r == t:
            return r
    return 0

def one():
    lines = aoc.get_lines(7)
    acc = 0
    for l in lines:
        acc += pl(l, ['+', '*'])
    print(acc)

def two():
    lines = aoc.get_lines(7)
    acc = 0
    for l in lines:
        acc += pl(l, ['+', '*', '||'])
    print(acc)

one()
two()

:::

Made a couple of attempts to munge the input data into some kind of binary search tree, lost some time to that, then threw my hands into the air and did a more naïve sort-of breadth-first search instead. Which turned out to be better for part 2 anyway.
Also, maths. Runs in just over a hundred milliseconds when using AsParallel, around half a second without.

::: spoiler C#

List<(long, int[])> data = new List<(long, int[])>();

public void Input(IEnumerable<string> lines)
{
  foreach (var line in lines)
  {
    var parts = line.Split(':', StringSplitOptions.TrimEntries);

    data.Add((long.Parse(parts.First()), parts.Last().Split(' ').Select(int.Parse).ToArray()));
  }
}

public void Part1()
{
  var correct = data.Where(kv => CalcPart(kv.Item1, kv.Item2)).Select(kv => kv.Item1).Sum();

  Console.WriteLine($"Correct: {correct}");
}
public void Part2()
{
  var correct = data.AsParallel().Where(kv => CalcPart2(kv.Item1, kv.Item2)).Select(kv => kv.Item1).Sum();

  Console.WriteLine($"Correct: {correct}");
}

public bool CalcPart(long res, Span<int> num, long carried = 0)
{
  var next = num[0];
  if (num.Length == 1)
    return res == carried + next || res == carried * next;
  return CalcPart(res, num.Slice(1), carried + next) || CalcPart(res, num.Slice(1), carried * next);
}

public bool CalcPart2(long res, Span<int> num, long carried = 0)
{
  var next = num[0];
  // Get the 10 logarithm for the next number, expand the carried value by 10^<next 10log + 1>, add the two together
  // For 123 || 45
  // 45 ⇒ 10log(45) + 1 == 2
  // 123 * 10^2 + 45 == 12345
  long combined = carried * (long)Math.Pow(10, Math.Floor(Math.Log10(next) + 1)) + next;
  if (num.Length == 1)
    return res == carried + next || res == carried * next || res == combined;
  return CalcPart2(res, num.Slice(1), carried + next) || CalcPart2(res, num.Slice(1), carried * next) || CalcPart2(res, num.Slice(1), combined);
}

I'm way behind, but I'm trying to learn F#.

I'm using the library Combinatorics in dotnet, which I've used in the past, generate in this case every duplicating possibility of the operations. I the only optimization that I did was to use a function to concatenate numbers without converting to strings, but that didn't actually help much.

I have parser helpers that use ReadOnlySpans over strings to prevent unnecessary allocations. However, here I'm adding to a C# mutable list and then converting to an FSharp (linked) list, which this language is more familiar with. Not optimal, but runtime was pretty good.

I'm not terribly good with F#, but I think I did ok for this challenge.

F#

// in another file:
let concatenateLong (a:Int64) (b:Int64) : Int64 =
    let rec countDigits (n:int64) =
        if n = 0 then 0
        else 1 + countDigits (n / (int64 10))   

    let bDigits = if b = 0 then 1 else countDigits b
    let multiplier = pown 10 bDigits |> int64
    a * multiplier + b

// challenge file
type Operation = {Total:Int64; Inputs:Int64 list }

let parse (s:ReadOnlySpan<char>) : Operation =
    let sep = s.IndexOf(':')
    let total = Int64.Parse(s.Slice(0, sep))
    let inputs = System.Collections.Generic.List<Int64>()
    let right:ReadOnlySpan<char> = s.Slice(sep + 1).Trim()

   // because the Split function on a span returns a SpanSplitEnumerator, which is a ref-struct and can only live on the stack, 
   // I can't use the F# list syntax here
    for range in right.Split(" ") do
        inputs.Add(Int64.Parse(sliceRange right range))
        
    {Total = total; Inputs = List.ofSeq(inputs) }

let part1Ops = [(+); (*)]

let execute ops input =
    input
    |> PSeq.choose (fun op ->
        let total = op.Total
        let inputs = op.Inputs
        let variations = Variations(ops, inputs.Length - 1, GenerateOption.WithRepetition)
        variations
        |> Seq.tryFind (fun v ->
            let calcTotal = (inputs[0], inputs[1..], List.ofSeq(v)) |||> List.fold2 (fun acc n f -> f acc n) 
            calcTotal = total
            )
        |> Option.map(fun _ -> total)
        )
    |> PSeq.fold (fun acc n -> acc + n) 0L

let part1 input =
    (read input parse)
    |> execute part1Ops

let part2Ops = [(+); (*); concatenateLong]

let part2 input = (read input parse) |> execute part2Ops

The Gen0 garbage collection looks absurd, but Gen0 is generally considered "free".

V2 - concatenate numbers did little for the runtime, but did help with Gen1 garbage, but not the overall allocation.

Julia

Took quite some time to debug but in the end I think it's a nice solution using base 2 and 3 numbers counting up to check all operator combinations.

::: spoiler Code

function readInput(inputFile::String)::Vector{Vector{Int}}
	f = open(inputFile,"r")
	lines::Vector{String} = readlines(f)
	close(f)
	equations::Vector{Vector{Int}} = []
	function getValues(line::String)
		return map(sp->parse(Int,sp),(sp=split(line," ");sp[1]=sp[1][1:end-1];sp))
	end
	map(l->push!(equations,getValues(l)),lines)
	return equations
end

function checkEq(eq::Vector{Int},withConCat::Bool)::Bool
	function calcEq(eq::Vector{Int},operators::Vector{Int},withConCat::Bool)::Int
		res::Int = eq[2]
		for (i,op) in enumerate(operators)
			if op == 0 #+
				res += eq[i+2]
			elseif op ==1 #*
				res *= eq[i+2]
			else #op==2 ||
				res = parse(Int,string(res)*string(eq[i+2]))
			end
		end
		return res
	end
	opInt::Int = 0
	operators = Vector{Int}(undef,length(eq)-2)
	while opInt < (withConCat ? 3^(length(eq)-2) : 2^(length(eq)-2))
		withConCat==true ? operators=digits(opInt,base=3,pad=length(eq)-2) : operators=digits(opInt,base=2,pad=length(eq)-2)
		#calcEq(eq,operators,withConCat)==eq[1] ? (return true) : opInt -= 1
		calcEq(eq,operators,withConCat)==eq[1] ? (return true) : opInt += 1
	end
	return false
end

function calcTotCalRes(equations::Vector{Vector{Int}},withConCat::Bool)::Int
	totCalRes::Int = 0
	for e in equations
		checkEq(e,withConCat) ? totCalRes+=e[1] : nothing
	end
	return totCalRes
end

@info "Part 1"
println("result: $(calcTotCalRes(readInput("day07Input"),false))")
@info "Part 2"
println("result: $(calcTotCalRes(readInput("day07Input"),true))")

:::

Kotlin

I finally got around to doing day 7. I try the brute force method (takes several seconds), but I'm particularly proud of my sequence generator for operation permutations.

The Collection#rotate method is in the file Utils.kt, which can be found in my repo.

::: spoiler Solution

import kotlin.collections.any
import kotlin.math.pow

fun main() {
    fun part1(input: List<String>): Long {
        val operations = setOf(CalibrationOperation.Plus, CalibrationOperation.Multiply)
        return generalizedSolution(input, operations)
    }

    fun part2(input: List<String>): Long {
        val operations = setOf(CalibrationOperation.Plus, CalibrationOperation.Multiply, CalibrationOperation.Concat)
        return generalizedSolution(input, operations)
    }

    val testInput = readInput("Day07_test")
    check(part1(testInput) == 3749L)
    check(part2(testInput) == 11387L)

    val input = readInput("Day07")
    part1(input).println()
    part2(input).println()
}

fun parseInputDay7(input: List<String>) = input.map {
    val calibrationResultAndInput = it.split(':')
    calibrationResultAndInput[0].toLong() to calibrationResultAndInput[1].split(' ').filter { it != "" }.map { it.toLong() }
}

fun generalizedSolution(input: List<String>, operations: Set<CalibrationOperation>): Long {
    val parsedInput = parseInputDay7(input)
    val operationsPermutations = CalibrationOperation.operationPermutationSequence(*operations.toTypedArray()).take(calculatePermutationsNeeded(parsedInput, operations)).toList()
    return sumOfPossibleCalibrationEquations(parsedInput, operationsPermutations)
}

fun calculatePermutationsNeeded(parsedInput: List<Pair<Long, List<Long>>>, operations: Set<CalibrationOperation>): Int {
    val highestNumberOfOperations = parsedInput.maxOf { it.second.size - 1 }
    return (1..highestNumberOfOperations).sumOf { operations.size.toDouble().pow(it).toInt() }
}

fun sumOfPossibleCalibrationEquations(parsedInput: List<Pair<Long, List<Long>>>, operationPermutationCollection: Collection<OperationPermutation>): Long {
    val permutationsGrouped = operationPermutationCollection.groupBy { it.size }
    return parsedInput.sumOf { (equationResult, equationInput) ->
        if (permutationsGrouped[equationInput.size - 1]!!.any { operations ->
                equationResult == equationInput.drop(1)
                    .foldIndexed(equationInput[0]) { index, acc, lng -> operations[index](acc, lng) }
            }) equationResult else 0
    }
}

typealias OperationPermutation = List<CalibrationOperation>

sealed class CalibrationOperation(val operation: (Long, Long) -> Long) {
    operator fun invoke(a: Long, b: Long) = operation(a, b)
    object Plus : CalibrationOperation({ a: Long, b: Long -> a + b })
    object Multiply : CalibrationOperation({ a: Long, b: Long -> a * b })
    object Concat : CalibrationOperation({ a: Long, b: Long -> "$a$b".toLong() })

    companion object {
        fun operationPermutationSequence(vararg operations: CalibrationOperation) = sequence<OperationPermutation> {
            val cache = mutableListOf<OperationPermutation>()
            val calculateCacheRange = { currentLength: Int ->
                val sectionSize = operations.size.toDouble().pow(currentLength - 1).toInt()
                val sectionStart = (1 until currentLength - 1).sumOf { operations.size.toDouble().pow(it).toInt() }
                sectionStart..(sectionStart + sectionSize - 1)
            }

            // Populate the cache with initial values for permutation length 1.
            operations.forEach { operation -> yield(listOf(operation).also { cache.add(it) }) }

            var currentLength = 2
            var offset = 0
            var cacheRange = calculateCacheRange(currentLength)
            var rotatingOperations = operations.toList()
            yieldAll(
                generateSequence {
                    if (cacheRange.count() == offset) {
                        rotatingOperations = rotatingOperations.rotated(1)
                        if (rotatingOperations.first() == operations.first()) {
                            currentLength++
                        }

                        offset = 0
                        cacheRange = calculateCacheRange(currentLength)
                    }

                    val cacheSlice = cache.slice(cacheRange)

                    return@generateSequence (cacheSlice[offset] + rotatingOperations.first()).also {
                        cache += it
                        offset++
                    } 
                }
            )
        }
    }
}

---

:::