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/day05.rs

@@ -1,9 +1,6 @@
 #![feature(iter_map_windows)]
 #![feature(test)]
-use std::{
-    cmp::max,
-    collections::VecDeque,
-};
+use std::{cmp::max, collections::VecDeque};
 
 use anyhow::Result;
 use aoc::Solver;

2023/src/bin/day14.rs

@@ -1,6 +1,10 @@
 #![feature(test)]
 
-use std::{fmt::Display, collections::{hash_map::DefaultHasher, HashMap}, hash::{Hash, Hasher}};
+use std::{
+    collections::{hash_map::DefaultHasher, HashMap},
+    fmt::Display,
+    hash::{Hash, Hasher},
+};
 
 use anyhow::Result;
 use aoc::Solver;
@@ -116,7 +120,7 @@ fn tilt_east(grid: &mut [Vec<Space>]) {
         for line in grid.iter_mut() {
             if line[x] == Space::Round {
                 let mut new_x = x;
-                for (xx, space) in line.iter().enumerate().skip(x+1) {
+                for (xx, space) in line.iter().enumerate().skip(x + 1) {
                     if space == &Space::Empty {
                         new_x = xx
                     } else {
@@ -140,7 +144,7 @@ fn tilt_south(grid: &mut Vec<Vec<Space>>) {
         for x in 0..width {
             if grid[y][x] == Space::Round {
                 let mut new_y = y;
-                for (yy, line) in grid.iter().enumerate().skip(y+1) {
+                for (yy, line) in grid.iter().enumerate().skip(y + 1) {
                     if line[x] == Space::Empty {
                         new_y = yy
                     } else {

2023/src/bin/day24.rs

@@ -1,10 +1,10 @@
 #![feature(test)]
 extern crate nalgebra as na;
-use std::{str::FromStr, convert::Infallible, collections::HashMap};
+use std::{collections::HashMap, convert::Infallible, str::FromStr};
 
 use anyhow::Result;
 use aoc::Solver;
-use na::{SMatrix, SVector};
+use na::{Matrix6, Vector6};
 
 // -- Runners --
 fn main() -> Result<()> {
@@ -56,7 +56,7 @@ struct Hailstone {
     pz: f64,
     vx: f64,
     vy: f64,
-    vz: f64
+    vz: f64,
 }
 
 impl Hailstone {
@@ -66,10 +66,11 @@ impl Hailstone {
 
         let d = self.vy * other.vx - self.vx * other.vy;
 
-        let t1 = (other.vy*dx - other.vx * dy) / d;
-        let t2 = (self.vy * dx - self.vx*dy) / d;
+        let t1 = (other.vy * dx - other.vx * dy) / d;
+        let t2 = (self.vy * dx - self.vx * dy) / d;
 
         if t1.is_sign_negative() || t2.is_sign_negative() {
+            // Intersection is in the past
             return None;
         }
 
@@ -77,32 +78,22 @@ impl Hailstone {
         let y = self.py + self.vy * t1;
 
         if x.is_infinite() || y.is_infinite() {
+            // Paths are parallel
             return None;
         }
 
         Some((x, y))
     }
-
-    fn is_parallel(&self, other: &Hailstone) -> bool {
-        let dx = self.px - other.px;
-        let dy = self.py - other.py;
-
-        let d = self.vy * other.vx - self.vx * other.vy;
-
-        let t1 = (other.vy*dx - other.vx * dy) / d;
-
-        let x = self.px + self.vx * t1;
-        let y = self.py + self.vy * t1;
-
-        x.is_infinite() && y.is_infinite()
-    }
 }
 
 impl FromStr for Hailstone {
     type Err = Infallible;
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let parts: Vec<f64> = s.split([',', '@']).map(|part| part.trim().parse().unwrap()).collect();
+        let parts: Vec<f64> = s
+            .split([',', '@'])
+            .map(|part| part.trim().parse().unwrap())
+            .collect();
 
         Ok(Hailstone {
             px: parts[0],
@@ -122,9 +113,11 @@ fn mode(numbers: &[usize]) -> usize {
         *occurrences.entry(value).or_insert(0) += 1;
     }
 
-    println!("{occurrences:?}");
-
-    occurrences.into_iter().max_by_key(|&(_, count)| count).map(|(value, _)| value).unwrap()
+    occurrences
+        .into_iter()
+        .max_by_key(|&(_, count)| count)
+        .map(|(value, _)| value)
+        .unwrap()
 }
 
 // -- Solution --
@@ -146,11 +139,19 @@ impl aoc::Solver for Day {
             200000000000000.0..=400000000000000.0
         };
 
-        hailstones.iter().enumerate().flat_map(|(index_a, a)| {
-            hailstones.iter().enumerate().filter(|(index_b, _)| index_b < &index_a).filter_map(|(_, b)| {
-                a.intersect_2d(b)
-            }).collect::<Vec<_>>()
-        }).filter(|&(x, y)| range.contains(&x) && range.contains(&y)).count()
+        hailstones
+            .iter()
+            .enumerate()
+            .flat_map(|(index_a, a)| {
+                hailstones
+                    .iter()
+                    .enumerate()
+                    .filter(|(index_b, _)| index_b < &index_a)
+                    .filter_map(|(_, b)| a.intersect_2d(b))
+                    .collect::<Vec<_>>()
+            })
+            .filter(|&(x, y)| range.contains(&x) && range.contains(&y))
+            .count()
     }
 
     fn part2(input: &str) -> Self::Output2 {
@@ -180,7 +181,8 @@ impl aoc::Solver for Day {
         let j = 1;
         // Due to numerical instability we run this with several different options for the third
         // hailstone
-        let solutions: Vec<_> = (2..h.len()).map(|k| {
+        let solutions: Vec<_> = (2..h.len())
+            .map(|k| {
                 // Constant in the matrix
                 let c1 = h[i].vz - h[j].vz;
                 let c2 = h[i].py - h[j].py;
@@ -197,35 +199,35 @@ impl aoc::Solver for Day {
                 let c12 = h[k].px - h[i].px;
 
                 // Setup the matrix
-            let matrix = SMatrix::<f64, 6, 6>::new(
-                0.0, c1, c3, 0.0, c4, c2,
-                -c1, 0.0, c5, -c4, 0.0, c6,
-                -c3, -c5, 0.0, -c2, -c6, 0.0,
-                0.0, c7, c9, 0.0, c10, c8,
-                -c7, 0.0, c11, -c10, 0.0, c12,
-                -c9, -c11, 0.0, -c8, -c12, 0.0
+                let matrix = Matrix6::new(
+                    0.0, c1, c3, 0.0, c4, c2, -c1, 0.0, c5, -c4, 0.0, c6, -c3, -c5, 0.0, -c2, -c6,
+                    0.0, 0.0, c7, c9, 0.0, c10, c8, -c7, 0.0, c11, -c10, 0.0, c12, -c9, -c11, 0.0,
+                    -c8, -c12, 0.0,
                 );
 
-            // Get the inverse of the matrix
-            let inverse = matrix.try_inverse().unwrap();
-
                 // Constant on the rhs
-            let k1 = h[i].py*h[i].vz - h[j].py*h[j].vz + h[j].pz*h[j].vy - h[i].pz*h[i].vy;
-            let k2 = h[i].pz*h[i].vx - h[j].pz*h[j].vx + h[j].px*h[j].vz - h[i].px*h[i].vz;
-            let k3 = h[i].px*h[i].vy - h[j].px*h[j].vy + h[j].py*h[j].vx - h[i].py*h[i].vx;
-            let k4 = h[i].py*h[i].vz - h[k].py*h[k].vz + h[k].pz*h[k].vy - h[i].pz*h[i].vy;
-            let k5 = h[i].pz*h[i].vx - h[k].pz*h[k].vx + h[k].px*h[k].vz - h[i].px*h[i].vz;
-            let k6 = h[i].px*h[i].vy - h[k].px*h[k].vy + h[k].py*h[k].vx - h[i].py*h[i].vx;
+                let k1 =
+                    h[i].py * h[i].vz - h[j].py * h[j].vz + h[j].pz * h[j].vy - h[i].pz * h[i].vy;
+                let k2 =
+                    h[i].pz * h[i].vx - h[j].pz * h[j].vx + h[j].px * h[j].vz - h[i].px * h[i].vz;
+                let k3 =
+                    h[i].px * h[i].vy - h[j].px * h[j].vy + h[j].py * h[j].vx - h[i].py * h[i].vx;
+                let k4 =
+                    h[i].py * h[i].vz - h[k].py * h[k].vz + h[k].pz * h[k].vy - h[i].pz * h[i].vy;
+                let k5 =
+                    h[i].pz * h[i].vx - h[k].pz * h[k].vx + h[k].px * h[k].vz - h[i].px * h[i].vz;
+                let k6 =
+                    h[i].px * h[i].vy - h[k].px * h[k].vy + h[k].py * h[k].vx - h[i].py * h[i].vx;
 
                 // Put them into a vector
-            let k = SVector::<f64, 6>::new(k1, k2, k3, k4, k5, k6);
+                let k = Vector6::new(k1, k2, k3, k4, k5, k6);
 
-            // Calclate the solution
-            let solution = inverse * k;
+                let solution = matrix.lu().solve(&k).unwrap();
 
                 // The sum of all elements of the starting position is the answer
                 (solution[0] + solution[1] + solution[2]).round() as usize
-        }).collect();
+            })
+            .collect();
 
         // The most common solution is the actual solution
         mode(&solutions)

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
+    }
+}