day 14 part 2

src/day14.rs

@@ -1,4 +1,9 @@
-use std::fs::read_to_string;
+use std::{
+    collections::HashSet,
+    fs::read_to_string,
+    io::{self, BufRead},
+    ops::Sub,
+};
 
 use itertools::Itertools;
 
@@ -12,11 +17,40 @@ pub fn day_main() {
 type RiddleResult = usize;
 
 fn part1(input: &str) -> RiddleResult {
-    solve(input, 100, 101, 103)
+    solve_part1(input, 100, 101, 103)
 }
 
-fn solve(input: &str, rounds: i64, width: i64, height: i64) -> RiddleResult {
-    let mut robots: Vec<((i64, i64), (i64, i64))> = input
+fn solve_part1(input: &str, rounds: i64, width: i64, height: i64) -> RiddleResult {
+    let mut robots = parse(input);
+    for _ in 0..rounds {
+        robots.iter_mut().for_each(|((px, py), (vx, vy))| {
+            *px = (*px + width + *vx) % width;
+            *py = (*py + height + *vy) % height;
+        });
+    }
+    let upper_left = robots
+        .iter()
+        .filter(|&&((px, py), _)| px < width / 2 && py < height / 2)
+        .count();
+    let lower_left = robots
+        .iter()
+        .filter(|&&((px, py), _)| px < width / 2 && py > height / 2)
+        .count();
+    let upper_right = robots
+        .iter()
+        .filter(|&&((px, py), _)| px > width / 2 && py < height / 2)
+        .count();
+    let lower_right = robots
+        .iter()
+        .filter(|&&((px, py), _)| px > width / 2 && py > height / 2)
+        .count();
+
+    if upper_left + lower_left == upper_right + lower_right {}
+    upper_left * lower_left * upper_right * lower_right
+}
+
+fn parse(input: &str) -> Vec<((i64, i64), (i64, i64))> {
+    input
         .lines()
         .map(|line| {
             line.strip_prefix("p=")
@@ -31,52 +65,66 @@ fn solve(input: &str, rounds: i64, width: i64, height: i64) -> RiddleResult {
                 .collect_tuple()
                 .unwrap()
         })
-        .collect_vec();
-    for _ in 0..rounds {
+        .collect_vec()
+}
+
+fn part2(input: &str) -> RiddleResult {
+    let width = 101;
+    let height = 103;
+    let mut robots = parse(input);
+    let mut seen = HashSet::new();
+    for second in 0.. {
+        if seen.contains(&robots) {
+            panic!("Loop after {second} rounds, but no christmas tree!");
+        }
+        seen.insert(robots.clone());
         robots.iter_mut().for_each(|((px, py), (vx, vy))| {
             *px = (*px + width + *vx) % width;
             *py = (*py + height + *vy) % height;
         });
-    }
-    // for y in 0..height {
-    //     for x in 0..width {
-    //         let c = robots
-    //             .iter()
-    //             .filter(|&&((px, py), _)| px == x && py == y)
-    //             .count();
-    //         if c == 0 {
-    //             print!(".");
-    //         } else {
-    //             print!("{c}");
-    //         }
-    //     }
-    //     println!();
-    // }
+
+        if robots
+            .iter()
+            .filter(|(s, _)| {
                 robots
                     .iter()
-        .filter(|&&((px, py), _)| px < width / 2 && py < height / 2)
-        .count()
-        * robots
-            .iter()
-            .filter(|&&((px, py), _)| px < width / 2 && py > height / 2)
-            .count()
-        * robots
-            .iter()
-            .filter(|&&((px, py), _)| px > width / 2 && py < height / 2)
-            .count()
-        * robots
-            .iter()
-            .filter(|&&((px, py), _)| px > width / 2 && py > height / 2)
+                    .any(|(t, _)| t != s && (t.0.sub(s.0).abs() + t.1.sub(s.1).abs()) <= 2)
+            })
             .count()
+            > robots.len() * 70 / 100
+        {
+            printr(&robots, width, height);
+            println!("after {} seconds. Press enter to continue or type 'merry christmas' if you can spot a tree!", second + 1); //+1 because we look at it after they have changed
+            let stdin = io::stdin();
+            let line = stdin.lock().lines().next().unwrap().unwrap();
+            if line.as_str().eq_ignore_ascii_case("merry christmas") {
+                return second + 1;
+            }
+        }
+    }
+    unreachable!()
 }
 
-fn part2(_input: &str) -> RiddleResult {
-    0
+fn printr(robots: &[((i64, i64), (i64, i64))], width: i64, height: i64) {
+    for y in 0..height {
+        for x in 0..width {
+            let c = robots
+                .iter()
+                .filter(|&&((px, py), _)| px == x && py == y)
+                .count();
+            if c == 0 {
+                print!(".");
+            } else {
+                print!("{c}");
+            }
+        }
+        println!();
+    }
 }
 
 #[cfg(test)]
 mod test {
-    use crate::day14::solve;
+    use crate::day14::solve_part1;
 
     use super::part2;
 
@@ -96,7 +144,7 @@ p=9,5 v=-3,-3
 
     #[test]
     fn test1() {
-        assert_eq!(solve(TEST_INPUT, 100, 11, 7), 12);
+        assert_eq!(solve_part1(TEST_INPUT, 100, 11, 7), 12);
     }
 
     #[test]