From a330505361416dc23a793633670c496c8a01eb27 Mon Sep 17 00:00:00 2001
From: Xiretza <xiretza@xiretza.xyz>
Date: Mon, 19 Dec 2022 19:29:01 +0100
Subject: [PATCH] 2022 day18/rust: add solution

---
 2022/day18/rust/Cargo.toml  |  11 +++
 2022/day18/rust/src/main.rs | 155 ++++++++++++++++++++++++++++++++++++
 Cargo.lock                  |   9 +++
 Cargo.toml                  |   1 +
 4 files changed, 176 insertions(+)
 create mode 100644 2022/day18/rust/Cargo.toml
 create mode 100644 2022/day18/rust/src/main.rs

diff --git a/2022/day18/rust/Cargo.toml b/2022/day18/rust/Cargo.toml
new file mode 100644
index 0000000..e06179c
--- /dev/null
+++ b/2022/day18/rust/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "rust_2022_18"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+aoc = { path = "../../../common/rust" }
+petgraph = "0.6.2"
+strum = "0.24.1"
diff --git a/2022/day18/rust/src/main.rs b/2022/day18/rust/src/main.rs
new file mode 100644
index 0000000..e0d72ce
--- /dev/null
+++ b/2022/day18/rust/src/main.rs
@@ -0,0 +1,155 @@
+#![warn(clippy::pedantic)]
+#![feature(generators)]
+#![feature(iter_from_generator)]
+#![feature(let_chains)]
+
+use petgraph::{algo::tarjan_scc, prelude::GraphMap, Undirected};
+use std::{io::stdin, iter};
+use strum::IntoEnumIterator;
+
+use aoc::vecn::{Direction3, VecN};
+
+type Position = VecN<3, u64>;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+struct Face {
+    position: Position,
+    side: Direction3,
+}
+
+impl Face {
+    fn facing(self) -> Option<Position> {
+        let pos = self.position.try_map(i64::try_from).ok()? + self.side.into();
+
+        pos.try_map(u64::try_from).ok()
+    }
+
+    fn inverse(self) -> Option<Face> {
+        Some(Face {
+            position: self.facing()?,
+            side: -self.side,
+        })
+    }
+
+    fn neighbours(self) -> impl Iterator<Item = (Angle, Face)> {
+        iter::from_generator(move || {
+            let orthogonal_sides =
+                Direction3::iter().filter(move |&side| side != self.side && side != -self.side);
+
+            for side in orthogonal_sides.clone() {
+                yield (
+                    Angle::Convex,
+                    Face {
+                        position: self.position,
+                        side,
+                    },
+                );
+            }
+
+            if let Some(facing) = self.facing() {
+                for side in orthogonal_sides.clone() {
+                    if let Some(inverse) = (Face {
+                        position: facing,
+                        side,
+                    })
+                    .inverse()
+                    {
+                        yield (Angle::Concave, inverse);
+                    }
+                }
+            }
+
+            for side in orthogonal_sides {
+                if let Some(facing) = (Face {
+                    position: self.position,
+                    side,
+                })
+                .facing()
+                {
+                    yield (
+                        Angle::Flat,
+                        Face {
+                            position: facing,
+                            side: self.side,
+                        },
+                    );
+                }
+            }
+        })
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum Angle {
+    Concave,
+    Convex,
+    Flat,
+}
+
+fn main() {
+    let cubes = stdin().lines().map(|l| l.unwrap().parse().unwrap());
+    let faces =
+        cubes.flat_map(|position| Direction3::iter().map(move |side| Face { position, side }));
+
+    let mut graph = GraphMap::<Face, Angle, Undirected>::new();
+    for face in faces {
+        if let Some(inverse) = face.inverse() {
+            if graph.remove_node(inverse) {
+                continue;
+            }
+        }
+
+        graph.add_node(face);
+
+        for (angle, neighbour_face) in face.neighbours() {
+            if graph.contains_node(neighbour_face) {
+                graph.add_edge(face, neighbour_face, angle);
+
+                if let Angle::Concave = angle {
+                    graph.remove_edge(
+                        face,
+                        Face {
+                            position: face.position,
+                            side: -neighbour_face.side,
+                        },
+                    );
+
+                    graph.remove_edge(
+                        neighbour_face,
+                        Face {
+                            position: neighbour_face.position,
+                            side: -face.side,
+                        },
+                    );
+                }
+            }
+        }
+    }
+
+    println!("{:?}", graph.node_count());
+
+    let sum_outside = tarjan_scc(&graph)
+        .into_iter()
+        .filter(|surface| {
+            graph
+                .all_edges()
+                .filter_map(|(start, end, angle)| {
+                    if surface.contains(&start) || surface.contains(&end) {
+                        Some(angle)
+                    } else {
+                        None
+                    }
+                })
+                .map(|angle| match angle {
+                    Angle::Concave => -1,
+                    Angle::Convex => 1,
+                    Angle::Flat => 0,
+                })
+                .sum::<i64>()
+                > 0
+        })
+        .map(|surface| surface.len())
+        .max()
+        .unwrap();
+    println!("{:?}", sum_outside);
+}
diff --git a/Cargo.lock b/Cargo.lock
index 9adcd0c..f4aa06b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -619,6 +619,15 @@ dependencies = [
  "aoc",
 ]
 
+[[package]]
+name = "rust_2022_18"
+version = "0.1.0"
+dependencies = [
+ "aoc",
+ "petgraph",
+ "strum",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.11"
diff --git a/Cargo.toml b/Cargo.toml
index ea046e5..b5da599 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,4 +25,5 @@ members = [
 	"2022/day13/rust",
 	"2022/day14/rust",
 	"2022/day15/rust",
+	"2022/day18/rust",
 ]