2023 - Day 25

2023/Cargo.toml

@@ -9,6 +9,7 @@ edition = "2021"
 anyhow = "1.0.75"
 lazy_static = "1.4.0"
 nalgebra = "0.32.3"
+petgraph = "0.6.4"
 regex = "1.10.2"
 
 [features]

2023/input/25/test-1

@@ -0,0 +1,13 @@
+jqt: rhn xhk nvd
+rsh: frs pzl lsr
+xhk: hfx
+cmg: qnr nvd lhk bvb
+rhn: xhk bvb hfx
+bvb: xhk hfx
+pzl: lsr hfx nvd
+qnr: nvd
+ntq: jqt hfx bvb xhk
+nvd: lhk
+lsr: lhk
+rzs: qnr cmg lsr rsh
+frs: qnr lhk lsr

2023/src/bin/day25.rs

@@ -0,0 +1,172 @@
+#![feature(test)]
+#![feature(iter_map_windows)]
+use std::collections::{HashMap, HashSet, VecDeque};
+
+use anyhow::Result;
+use aoc::Solver;
+use petgraph::{
+    algo::{condensation, has_path_connecting},
+    graphmap::{GraphMap, UnGraphMap},
+    visit::IntoNodeReferences,
+    Undirected,
+};
+
+// -- Runners --
+fn main() -> Result<()> {
+    Day::solve()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_test1() -> Result<()> {
+        Day::test(Day::part1, "test-1", 54)
+    }
+
+    #[test]
+    fn part1_solution() -> Result<()> {
+        Day::test(Day::part1, "input", 552695)
+    }
+
+    // Benchmarks
+    extern crate test;
+    #[bench]
+    #[ignore]
+    fn part1_bench(b: &mut test::Bencher) {
+        Day::benchmark(Day::part1, b)
+    }
+    #[bench]
+    #[ignore]
+    fn part2_bench(b: &mut test::Bencher) {
+        Day::benchmark(Day::part2, b)
+    }
+}
+
+// Totally copied this from: https://github.com/Zemogus/AOC-2023/blob/328dc6618f3a360c3d3851ad1b10513a6c133336/src/day25.rs
+// For some reason the graph library has no dijkstra that returns the actual path
+fn find_shortest_path<'a>(
+    graph: &GraphMap<&'a str, (), Undirected>,
+    start: &'a str,
+    end: &'a str,
+) -> Option<Vec<&'a str>> {
+    let mut queue = VecDeque::new();
+    let mut visited = HashSet::new();
+    let mut parents = HashMap::new();
+
+    queue.push_back(start);
+    while let Some(node) = queue.pop_front() {
+        // Already visited this node
+        if !visited.insert(node) {
+            continue;
+        }
+
+        // Reached the destination
+        if node == end {
+            break;
+        }
+
+        for neighbour in graph.neighbors(node) {
+            if !visited.contains(neighbour) {
+                parents.insert(neighbour, node);
+                queue.push_back(neighbour);
+            }
+        }
+    }
+
+    let mut path = Vec::new();
+    let mut node = end;
+    while node != start {
+        path.push(node);
+        if let Some(parent) = parents.get(&node) {
+            node = parent;
+        } else {
+            return None;
+        }
+    }
+
+    path.push(start);
+
+    Some(path)
+}
+
+// -- Solution --
+pub struct Day;
+impl aoc::Solver for Day {
+    type Output1 = usize;
+    type Output2 = usize;
+
+    fn day() -> u8 {
+        25
+    }
+
+    fn part1(input: &str) -> Self::Output1 {
+        // Create a list of all edges
+        let edges: Vec<_> = input
+            .lines()
+            .flat_map(|line| {
+                let (a, rest) = line.split_once(": ").unwrap();
+                rest.split(' ').map(|b| (a, b)).collect::<Vec<_>>()
+            })
+            .collect();
+
+        // Create a graph from all the edges
+        let graph = UnGraphMap::<_, ()>::from_edges(edges);
+
+        // Take a node as the starting point
+        let start = graph.nodes().next().unwrap();
+        // Loop over all other nodes
+        for end in graph.nodes() {
+            // Make a copy of the graph so we can modify it and undo changes later
+            let mut graph = graph.clone();
+            if start == end {
+                continue;
+            }
+
+            // If the two nodes are on the same side there should be more then three paths
+            // connecting the nodes together
+            // At least I think???
+            // This solution worked, so ¯\_(ツ)_/¯
+            for _ in 0..3 {
+                // Find the current shortest path
+                let path = find_shortest_path(&graph, start, end).unwrap();
+
+                // Remove the path
+                for slice in path.windows(2) {
+                    match slice {
+                        [a, b] => graph.remove_edge(a, b),
+                        _ => unreachable!(
+                            "There should be three paths connecting all the nodes together"
+                        ),
+                    };
+                }
+            }
+
+            // If there is no path connecting the two nodes we have removed the three edges
+            // connecting the two halves
+            if !has_path_connecting(&graph, start, end, None) {
+                // Condense the graph, creates a new graph where each node contains all nodes that
+                // where connected in the input node
+                let condensed = condensation(graph.into_graph::<usize>(), false);
+
+                // The should give us two nodes each containing all the nodes in their respective
+                // half if we split the graph
+                if condensed.node_count() != 2 {
+                    continue;
+                }
+
+                // Multiply the size of each of the halves together giving the final solution
+                return condensed
+                    .node_references()
+                    .fold(1, |acc, (_, nodes)| acc * nodes.len());
+            }
+        }
+
+        unreachable!("No solution found");
+    }
+
+    fn part2(_input: &str) -> Self::Output2 {
+        0
+    }
+}