2022 day12/rust: add solution

2022/data/day12.expected

@@ -0,0 +1,2 @@
+504
+500

2022/data/day12.input

@@ -0,0 +1,41 @@
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+abccccccccccccccccccccaaaaacccccccccaaccccccccaaaaaacccccccccaaaaaaaaaaaaaaaacccccccccccccccaaaacccccccccaacccccccccccccccccccccccccccccccccccccccccccccccaaaaa

2022/day12/rust/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "rust_2022_12"
+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"

2022/day12/rust/src/main.rs

@@ -0,0 +1,93 @@
+#![warn(clippy::pedantic)]
+
+use std::io::{stdin, Read};
+
+use petgraph::{
+    algo::k_shortest_path,
+    graph::{Graph, NodeIndex},
+    visit::IntoNodeReferences,
+};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum NodeKind {
+    Start,
+    End,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+struct NodeData {
+    kind: Option<NodeKind>,
+    height: u32,
+}
+
+fn main() {
+    let mut data = String::new();
+    stdin().read_to_string(&mut data).unwrap();
+
+    // graph of "downhill" edges - edge from A to B means that A is reachable from B
+    let mut graph = Graph::<NodeData, (), _>::new();
+
+    let grid: Vec<Vec<NodeIndex>> = data
+        .lines()
+        .map(|line| {
+            line.chars()
+                .map(|c| {
+                    let (kind, c) = match c {
+                        'S' => (Some(NodeKind::Start), 'a'),
+                        'E' => (Some(NodeKind::End), 'z'),
+                        c => (None, c),
+                    };
+
+                    let height = u32::from(c) - u32::from('a');
+                    let data = NodeData { kind, height };
+                    graph.add_node(data)
+                })
+                .collect()
+        })
+        .collect();
+
+    for (x, row) in grid.iter().enumerate() {
+        for (y, &node_id) in row.iter().enumerate() {
+            let node = graph[node_id];
+
+            let x = i32::try_from(x).unwrap();
+            let y = i32::try_from(y).unwrap();
+            let neighbours = [(-1i32, 0), (0, -1), (1, 0), (0, 1)]
+                .into_iter()
+                .filter_map(|(dx, dy)| {
+                    let x = usize::try_from(x + dx).ok()?;
+                    let y = usize::try_from(y + dy).ok()?;
+                    grid.get(x)?.get(y)
+                });
+
+            for &neighbour_id in neighbours {
+                let neighbour = graph[neighbour_id];
+                if node.height <= (neighbour.height + 1) {
+                    // `node` is reachable from `neighbour`
+                    graph.add_edge(node_id, neighbour_id, ());
+                }
+            }
+        }
+    }
+
+    let end = graph
+        .node_references()
+        .find_map(|(id, node)| (node.kind == Some(NodeKind::End)).then_some(id))
+        .unwrap();
+    let paths = k_shortest_path(&graph, end, None, 1, |_| 1);
+
+    let start = graph
+        .node_references()
+        .find_map(|(id, node)| (node.kind == Some(NodeKind::Start)).then_some(id))
+        .unwrap();
+    println!("{:?}", paths[&start]);
+
+    println!(
+        "{:?}",
+        paths
+            .into_iter()
+            .filter_map(|(start_id, steps)| (graph[start_id].height == 0).then_some(steps))
+            .min()
+            .unwrap()
+    );
+}

Cargo.lock

@@ -192,12 +192,24 @@ version = "1.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "90e5c1c8368803113bf0c9584fc495a58b86dc8a29edbf8fe877d21d9507e797"
 
+[[package]]
+name = "fixedbitset"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0ce7134b9999ecaf8bcd65542e436736ef32ddca1b3e06094cb6ec5755203b80"
+
 [[package]]
 name = "half"
 version = "1.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "eabb4a44450da02c90444cf74558da904edde8fb4e9035a9a6a4e15445af0bd7"
 
+[[package]]
+name = "hashbrown"
+version = "0.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8a9ee70c43aaf417c914396645a0fa852624801b24ebb7ae78fe8272889ac888"
+
 [[package]]
 name = "hermit-abi"
 version = "0.1.19"
@@ -207,6 +219,16 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "indexmap"
+version = "1.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1885e79c1fc4b10f0e172c475f458b7f7b93061064d98c3293e98c5ba0c8b399"
+dependencies = [
+ "autocfg",
+ "hashbrown",
+]
+
 [[package]]
 name = "itertools"
 version = "0.10.5"
@@ -320,6 +342,16 @@ version = "11.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0ab1bc2a289d34bd04a330323ac98a1b4bc82c9d9fcb1e66b63caa84da26b575"
 
+[[package]]
+name = "petgraph"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6d5014253a1331579ce62aa67443b4a658c5e7dd03d4bc6d302b94474888143"
+dependencies = [
+ "fixedbitset",
+ "indexmap",
+]
+
 [[package]]
 name = "plotters"
 version = "0.3.4"
@@ -545,6 +577,14 @@ dependencies = [
  "aoc",
 ]
 
+[[package]]
+name = "rust_2022_12"
+version = "0.1.0"
+dependencies = [
+ "aoc",
+ "petgraph",
+]
+
 [[package]]
 name = "ryu"
 version = "1.0.11"

Cargo.toml

@@ -21,4 +21,5 @@ members = [
 	"2022/day9/rust",
 	"2022/day10/rust",
 	"2022/day11/rust",
+	"2022/day12/rust",
 ]