day 18 performance improvement

src/day18.rs

@@ -1,10 +1,9 @@
-use std::{
-    collections::{HashMap, HashSet, VecDeque},
-    fs::read_to_string,
-};
+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();
@@ -18,30 +17,33 @@ fn part1(input: &str) -> RiddleResult {
     solve1(input, 1024, 70)
 }
 
-fn solve1(input: &str, n: usize, coord_max: i32) -> usize {
+fn solve1(input: &str, n: usize, coord_max: i64) -> usize {
     let points = parse(input);
     sp(&points[..n], coord_max).unwrap()
 }
 
-fn sp(points: &[(i32, i32)], coord_max: i32) -> Option<usize> {
-    let pointss: HashSet<&(i32, i32)> = HashSet::from_iter(points);
-    let mut visited = HashMap::new();
+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.contains_key(&(x, y)) {
+        if visited.get((x, y)) == Some(&true) {
             continue;
         }
-        visited.insert((x, y), c);
+        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)
-                && !pointss.contains(&(a, b))
+                && pcheck.get((a, b)) == Some(&false)
             {
                 queue.push_back((a, b, c + 1));
             }
@@ -50,7 +52,7 @@ fn sp(points: &[(i32, i32)], coord_max: i32) -> Option<usize> {
     None
 }
 
-fn parse(input: &str) -> Vec<(i32, i32)> {
+fn parse(input: &str) -> Vec<(i64, i64)> {
     input
         .trim()
         .lines()
@@ -67,14 +69,39 @@ fn part2(input: &str) -> String {
     solve2(input, 1024, 70)
 }
 
-fn solve2(input: &str, fixed: usize, max_coord: i32) -> String {
+fn solve2(input: &str, fixed: usize, max_coord: i64) -> String {
     let points = parse(input);
-    for i in fixed..points.len() {
-        if let None = sp(&points[..=i], max_coord) {
-            return format!("{},{}", points[i].0, points[i].1);
+
+    // 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;
         }
     }
-    unreachable!()
 }
 
 #[cfg(test)]

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/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),
@@ -29,17 +30,20 @@ fn main() {
         (23, day23::day_main),
         (24, day24::day_main),
         (25, day25::day_main),
-        (18, day18::day_main),
         // PLACEHOLDER
     ]);
     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;
     };