day 18 performance improvement

README.md

@@ -1,3 +1,9 @@
 # Advent of Rust 2024
 
 A few of the solutions for [Advent of Code 2024](https://adventofcode.com/2024) in Rust.
+
+## Points
+
+I finally (as of October 2025) finished all existing puzzles and am a part of the 500 star club!
+
+![Screenshot from Advent of Code saying "Totals stars: 500"](assets/500stars.png)

src/day18.rs

@@ -0,0 +1,147 @@
+use std::{collections::VecDeque, fs::read_to_string};
+
+use itertools::Itertools;
+
+use crate::utils::grid::Grid;
+
+pub fn day_main() {
+    let input = read_to_string("input/day18.txt").unwrap();
+    let input = input.trim();
+    println!(" part1: {}", part1(input));
+    println!(" part2: {}", part2(input));
+}
+
+type RiddleResult = usize;
+
+fn part1(input: &str) -> RiddleResult {
+    solve1(input, 1024, 70)
+}
+
+fn solve1(input: &str, n: usize, coord_max: i64) -> usize {
+    let points = parse(input);
+    sp(&points[..n], coord_max).unwrap()
+}
+
+fn sp(points: &[(i64, i64)], coord_max: i64) -> Option<usize> {
+    let mut pcheck = Grid::from_default(coord_max + 1, coord_max + 1);
+    for p in points {
+        pcheck.set(*p, true);
+    }
+    let mut visited = Grid::from_default(coord_max + 1, coord_max + 1);
+    let mut queue = VecDeque::from_iter([(0, 0, 0)]);
+    while let Some((x, y, c)) = queue.pop_front() {
+        if x == coord_max && y == coord_max {
+            return Some(c);
+        }
+
+        if visited.get((x, y)) == Some(&true) {
+            continue;
+        }
+        visited.set((x, y), true);
+
+        for (dx, dy) in [(0, 1), (1, 0), (0, -1), (-1, 0)] {
+            let (a, b) = (x + dx, y + dy);
+            if (0..=coord_max).contains(&a)
+                && (0..=coord_max).contains(&b)
+                && pcheck.get((a, b)) == Some(&false)
+            {
+                queue.push_back((a, b, c + 1));
+            }
+        }
+    }
+    None
+}
+
+fn parse(input: &str) -> Vec<(i64, i64)> {
+    input
+        .trim()
+        .lines()
+        .map(|line| {
+            line.split(",")
+                .map(|v| v.parse().unwrap())
+                .collect_tuple()
+                .unwrap()
+        })
+        .collect_vec()
+}
+
+fn part2(input: &str) -> String {
+    solve2(input, 1024, 70)
+}
+
+fn solve2(input: &str, fixed: usize, max_coord: i64) -> String {
+    let points = parse(input);
+
+    // we want the first point with which there is no shortest path
+    let mut i = fixed;
+    let mut jump = (points.len() - fixed) / 2;
+    #[cfg(debug_assertions)]
+    let mut loops = 0;
+    loop {
+        #[cfg(debug_assertions)]
+        {
+            loops += 1;
+        }
+        let l = sp(&points[..i - 1], max_coord);
+        let r = sp(&points[..i], max_coord);
+        if l.is_some() && r.is_none() {
+            #[cfg(debug_assertions)]
+            {
+                let iters_needed = i - fixed;
+                dbg!(loops, iters_needed);
+            }
+            return format!("{},{}", points[i - 1].0, points[i - 1].1);
+        }
+        if l.is_some() {
+            i += jump;
+        } else {
+            i -= jump;
+        }
+        jump /= 2;
+        if jump == 0 {
+            jump += 1;
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::day18::{solve1, solve2};
+
+    const TEST_INPUT: &str = r"5,4
+4,2
+4,5
+3,0
+2,1
+6,3
+2,4
+1,5
+0,6
+3,3
+2,6
+5,1
+1,2
+5,5
+2,5
+6,5
+1,4
+0,4
+6,4
+1,1
+6,1
+1,0
+0,5
+1,6
+2,0
+";
+
+    #[test]
+    fn test1() {
+        assert_eq!(solve1(TEST_INPUT, 12, 6), 22);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(solve2(TEST_INPUT, 12, 6), "6,1");
+    }
+}

src/day21.rs

@@ -276,19 +276,19 @@ mod test {
 
     #[test]
     fn shortest_human() {
-        let precomputed = Precomputed::new(2);
+        let mut precomputed = Precomputed::new(2);
         assert_eq!(precomputed.get('<', '^', 0), 1);
     }
 
     #[test]
     fn shortest_1st() {
-        let p = Precomputed::new(2);
+        let mut p = Precomputed::new(2);
         assert_eq!(p.get('A', '^', 1), 2);
     }
 
     #[test]
     fn shortest_2nd() {
-        let p = Precomputed::new(2);
+        let mut p = Precomputed::new(2);
         assert_eq!(p.get('A', '^', 2), 8);
     }
 

src/day23.rs

@@ -28,7 +28,6 @@ fn part1(input: &str) -> RiddleResult {
         }
     }
     let sets = sets.iter().unique().collect_vec();
-    dbg!(sets.len());
     sets.iter()
         .filter(|set| set.iter().any(|t| t.starts_with("t")))
         .count()

src/lib.rs

@@ -15,6 +15,7 @@ pub mod day14;
 pub mod day15;
 pub mod day16;
 pub mod day17;
+pub mod day18;
 pub mod day19;
 pub mod day21;
 pub mod day22;

src/main.rs

@@ -22,6 +22,7 @@ fn main() {
         (15, day15::day_main),
         (16, day16::day_main),
         (17, day17::day_main),
+        (18, day18::day_main),
         (19, day19::day_main),
         (21, day21::day_main),
         (22, day22::day_main),
@@ -33,12 +34,16 @@ fn main() {
     ]);
     let day: Option<u8> = args().nth(1).and_then(|a| a.parse().ok());
     let Some(day) = day else {
+        let start = Instant::now();
         mains
             .iter()
             .sorted_by_key(|entry| entry.0)
             .for_each(|(d, f)| {
                 run(*d, f);
             });
+        let duration = start.elapsed();
+        println!();
+        println!("{COLOR}{ITALIC}All tasks took {duration:?}{RESET_FORMATTING}");
         return;
     };