day25: problem 1 solution - cheated with dot

25/src/main.rs

@@ -0,0 +1,171 @@
+use indicatif::{ProgressBar, ProgressIterator, ProgressStyle};
+use itertools::Itertools;
+use petgraph::algo::connected_components;
+use petgraph::dot::Dot;
+use petgraph::prelude::*;
+use petgraph::visit::{depth_first_search, DfsEvent, IntoEdgeReferences, IntoNodeIdentifiers, IntoNodeReferences};
+use rayon::prelude::*;
+use std::collections::HashMap;
+use std::fs::File;
+use std::io::{BufRead, BufReader, Lines};
+use std::time::Instant;
+
+// BOILERPLATE
+type InputIter = Lines<BufReader<File>>;
+
+fn get_input() -> InputIter {
+    let f = File::open("input").unwrap();
+    let br = BufReader::new(f);
+    br.lines()
+}
+
+fn main() {
+    let start = Instant::now();
+    let ans1 = problem1(get_input());
+    let duration = start.elapsed();
+    println!("Problem 1 solution: {} [{}s]", ans1, duration.as_secs_f64());
+
+    let start = Instant::now();
+    let ans2 = problem2(get_input());
+    let duration = start.elapsed();
+    println!("Problem 2 solution: {} [{}s]", ans2, duration.as_secs_f64());
+}
+
+// PARSE
+
+struct Circuit {
+    graph: UnGraph<String, String>,
+    nodes: HashMap<String, Node>,
+}
+
+#[derive(Debug, Clone)]
+struct Node {
+    targets: Vec<String>,
+    index: Option<NodeIndex>,
+}
+
+impl Node {
+    fn with_index(mut self, index: NodeIndex) -> Self {
+        self.index = Some(index);
+        self
+    }
+}
+
+impl<T: BufRead> From<Lines<T>> for Circuit {
+    fn from(lines: Lines<T>) -> Self {
+        let mut graph = UnGraph::default();
+        let mut nodes = HashMap::new();
+        for line in lines.map(|v| v.unwrap()) {
+            let (source, targets_s) = line.split_once(": ").unwrap();
+            let targets = targets_s.split_whitespace().map(|s| s.to_string()).collect_vec();
+            nodes.insert(
+                source.to_string(),
+                Node {
+                    targets,
+                    index: Some(graph.add_node(source.to_string())),
+                },
+            );
+        }
+
+        for (name, node) in nodes.iter_mut() {
+            for target in &node.targets {
+                let target_idx = match graph.node_references().find(|n| n.1 == target).map(|n| n.0) {
+                    Some(target) => target,
+                    None => graph.add_node(target.to_string()),
+                };
+                graph.add_edge(node.index.unwrap(), target_idx, format!("{}-{}", name, target));
+            }
+        }
+
+        Self { graph, nodes }
+    }
+}
+
+impl Circuit {
+    // returns the set of nodes on each side
+    fn find_critical_edges(&self, removals: usize) -> (Vec<String>, Vec<String>) {
+        let bar = ProgressBar::new(self.graph.edge_references().combinations(removals).try_len().unwrap() as u64)
+            .with_style(
+                ProgressStyle::with_template(
+                    "[{elapsed_precise}/{eta_precise}] {bar:40.cyan/blue} {pos:>7}/{len:7} {per_sec}",
+                )
+                .unwrap(),
+            );
+        // for set in self.graph.edge_references().combinations(removals).progress_with(bar) {
+        
+        let set = [("zcp", "zjm"), ("rsg", "nsk"), ("jks", "rfg")]
+            .iter()
+            .flat_map(|(src, dst)| {
+                self.graph.edge_references().filter(|e| self.graph[e.source()] == *src && self.graph[e.target()] == *dst || self.graph[e.target()] == *src && self.graph[e.source()] == *dst)
+            }).collect_vec();
+        let mut local_graph: StableUnGraph<_, _> = self.graph.clone().into();
+        for wire in &set {
+            local_graph.remove_edge(wire.id());
+        }
+        let local_graph = UnGraph::from(local_graph);
+        if connected_components(&local_graph) == 2 {
+            // each edge will have one leg in each component, so return the set of connected nodes
+            let mut left = Vec::new();
+            depth_first_search(&local_graph, Some(set[0].source()), |event| {
+                if let DfsEvent::Discover(n, t) = event {
+                    left.push(local_graph[n].to_string());
+                }
+            });
+            let mut right = Vec::new();
+            depth_first_search(&local_graph, Some(set[0].target()), |event| {
+                if let DfsEvent::Discover(n, t) = event {
+                    right.push(local_graph[n].to_string());
+                }
+            });
+            return (left, right);
+        }
+        // }
+        panic!("no cutline found");
+    }
+}
+
+// PROBLEM 1 solution
+
+fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
+    let circuit = Circuit::from(input);
+    println!("{:?}", Dot::new(&circuit.graph));
+    let (left, right) = circuit.find_critical_edges(3);
+    (left.len() * right.len()) as u64
+}
+
+// PROBLEM 2 solution
+fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
+    0
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::*;
+    use std::io::Cursor;
+
+    const EXAMPLE: &str = &"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";
+
+    #[test]
+    fn problem1_example() {
+        let c = Cursor::new(EXAMPLE);
+        assert_eq!(problem1(c.lines()), 54);
+    }
+
+    #[test]
+    fn problem2_example() {
+        let c = Cursor::new(EXAMPLE);
+        assert_eq!(problem2(c.lines()), 0);
+    }
+}