From 396c9730003e259324ee223bf0fbd5bfbd154470 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20M=C3=BCller?= <stefan.muller@ubisoft.com>
Date: Mon, 13 Jul 2026 21:19:41 +0200
Subject: [PATCH] Add solution for "Day 10: Factory", part 1

---
 Cargo.lock             | 16 ++++++++++
 Cargo.toml             |  1 +
 src/main.rs            |  2 +-
 src/solvers.rs         |  1 +
 src/solvers/factory.rs | 67 ++++++++++++++++++++++++++++++++++++++++++
 tests/examples.rs      |  8 +++++
 tests/full_data.rs     |  8 +++++
 7 files changed, 102 insertions(+), 1 deletion(-)
 create mode 100644 src/solvers/factory.rs

diff --git a/Cargo.lock b/Cargo.lock
index 8c48120..b7ca8be 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -9,6 +9,7 @@ dependencies = [
  "bitflags",
  "grapherity",
  "grid",
+ "itertools",
  "memchr",
  "primes",
  "sanitise-file-name",
@@ -42,6 +43,12 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
+[[package]]
+name = "either"
+version = "1.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "91622ff5e7162018101f2fea40d6ebf4a78bbe5a49736a2020649edf9693679e"
+
 [[package]]
 name = "grapherity"
 version = "0.2.1"
@@ -57,6 +64,15 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b40ca9252762c466af32d0b1002e91e4e1bc5398f77455e55474deb466355ff5"
 
+[[package]]
+name = "itertools"
+version = "0.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b4baf93f58d4425749ca49a51c50ebab072c5df6994d08fed93541c331481dc"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "memchr"
 version = "2.8.2"
diff --git a/Cargo.toml b/Cargo.toml
index 0e1217b..a584d9d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2024"
 bitflags = "2.13.0"
 grapherity = "0.2.1"
 grid = "1.0.0"
+itertools = "0.15.0"
 memchr = "2.7.6"
 primes = "0.4.0"
 sanitise-file-name = "1.0.0"
diff --git a/src/main.rs b/src/main.rs
index a063ce1..9603d06 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -11,7 +11,7 @@ fn main() {
     solvers::run(solvers::laboratories::Laboratories {});
     solvers::run(solvers::playground::Playground::new(None));
     solvers::run(solvers::movie_theater::MovieTheater {});
-    // Factory
+    solvers::run(solvers::factory::Factory {});
     // Reactor
     // ChristmasTreeFarm
 }
diff --git a/src/solvers.rs b/src/solvers.rs
index f7de0de..ddc0fb3 100644
--- a/src/solvers.rs
+++ b/src/solvers.rs
@@ -6,6 +6,7 @@ use std::path;
 use std::path::Path;
 
 pub mod cafeteria;
+pub mod factory;
 pub mod gift_shop;
 pub mod laboratories;
 pub mod lobby;
diff --git a/src/solvers/factory.rs b/src/solvers/factory.rs
new file mode 100644
index 0000000..4474e5c
--- /dev/null
+++ b/src/solvers/factory.rs
@@ -0,0 +1,67 @@
+use crate::solvers::Solver;
+use itertools::Itertools;
+use std::io::BufRead;
+
+pub struct Factory {}
+
+impl Factory {
+    const INDICATOR_ON_CHAR: u8 = b'#';
+
+    // Turns a string like "[..##.]", interpreted as a binary number with low-significance bit left, into a decimal
+    // integer, e.g. 0 * 1 + 0 * 2 + 1 * 4 + 1 * 8 + 0 * 16 = 12.
+    fn indicators(s: &str) -> u16 {
+        s.bytes()
+            .enumerate()
+            .filter(|&(_, c)| c == Self::INDICATOR_ON_CHAR)
+            .fold(0, |acc, (i, _)| acc + (1 << (i - 1)))
+    }
+
+    // Turns a string like "(0,3,4)", interpreted as the set of digits of a binary number that are one, into a decimal
+    // integer, e.g. 2^0 + 2^3 + 2^4 = 25.
+    fn button(s: &str) -> u16 {
+        s[1..s.len() - 1]
+            .split(',')
+            .map(|b| b.parse().expect("button index should be a number"))
+            .fold(0, |acc, x| acc + 2_u16.pow(x))
+    }
+
+    fn find_min_button_presses(indicators: u16, buttons: &[u16]) -> u64 {
+        if buttons.contains(&indicators) {
+            1
+        } else {
+            let len = buttons.len();
+            for k in 2..len {
+                if buttons
+                    .iter()
+                    .combinations(k)
+                    .any(|combination| combination.iter().fold(0, |acc, &x| acc ^ x) == indicators)
+                {
+                    return k as u64;
+                }
+            }
+            len as u64
+        }
+    }
+}
+
+impl Solver for Factory {
+    const PUZZLE_INDEX: u8 = 10;
+    const PUZZLE_NAME: &'static str = "Factory";
+
+    fn process_data<R: BufRead>(&self, reader: R) -> (u64, u64) {
+        let mut part1 = 0;
+        let mut buttons = Vec::new();
+        for line in reader.lines().map_while(Result::ok) {
+            buttons.clear();
+            let mut split = line.split(' ').into_iter();
+            let indicators = Self::indicators(split.next().expect("missing indicator lights"));
+            let mut current = split.next().expect("missing button wiring schematics");
+            while let Some(next) = split.next() {
+                buttons.push(Self::button(current));
+                current = next;
+            }
+            part1 += Self::find_min_button_presses(indicators, &buttons);
+        }
+        (part1, 0)
+    }
+}
diff --git a/tests/examples.rs b/tests/examples.rs
index 7e6906f..1edcf56 100644
--- a/tests/examples.rs
+++ b/tests/examples.rs
@@ -85,3 +85,11 @@ fn movie_theater() {
         solvers::run_solver(solvers::movie_theater::MovieTheater {}, &EXAMPLE_PATHS)
     );
 }
+
+#[test]
+fn factory() {
+    assert_eq!(
+        Ok((7, 0)),
+        solvers::run_solver(solvers::factory::Factory {}, &EXAMPLE_PATHS)
+    );
+}
diff --git a/tests/full_data.rs b/tests/full_data.rs
index c9d696a..613764c 100644
--- a/tests/full_data.rs
+++ b/tests/full_data.rs
@@ -86,3 +86,11 @@ fn movie_theater() {
         )
     );
 }
+
+#[test]
+fn factory() {
+    assert_eq!(
+        Ok((409, 0)),
+        solvers::run_solver(solvers::factory::Factory {}, &solvers::DATA_PATHS)
+    );
+}