day04 and benchmarks

.cargo/config.toml

@@ -10,3 +10,6 @@ time = "run --quiet --release -- time"
 
 [env]
 AOC_YEAR = "2025"
+
+[http]
+check-revoke = false

README.md

@@ -13,8 +13,10 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | :---: | :---: | :---:  |
 | [Day 1](./src/bin/01.rs) | `881.1µs` | `849.0µs` |
 | [Day 2](./src/bin/02.rs) | `225.7ms` | `250.4ms` |
+| [Day 3](./src/bin/03.rs) | `85.9µs` | `120.1µs` |
+| [Day 4](./src/bin/04.rs) | `227.4µs` | `1.9ms` |
 
-**Total: 477.83ms**
+**Total: 480.16ms**
 <!--- benchmarking table --->
 
 ---

data/examples/04.txt

@@ -0,0 +1,10 @@
+..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.

src/bin/03.rs

@@ -36,7 +36,7 @@ pub fn part_one(input: &str) -> Option<u64> {
         total += get_joltage(line, 2).unwrap();
     }
 
-    println!("Total: {}", total);
+    // println!("Total: {}", total);
     Some(total)
 }
 
@@ -46,7 +46,7 @@ pub fn part_two(input: &str) -> Option<u64> {
         total += get_joltage(line, 12).unwrap();
     }
 
-    println!("Total: {}", total);
+    // println!("Total: {}", total);
     Some(total)
 }
 

src/bin/04.rs

@@ -0,0 +1,118 @@
+advent_of_code::solution!(4);
+use core::iter::Iterator;
+
+use itertools::Itertools;
+
+#[derive(PartialEq)]
+enum Item {
+    Empty,
+    Roll
+}
+
+const DIRECTIONS: &[(isize, isize); 8] = &[
+    (-1, -1), (-1, 0), (-1, 1),
+    (0, -1),          (0, 1),
+    (1, -1),  (1, 0), (1, 1),
+];
+
+fn roll_count(grid: &Vec<Vec<Item>>, row_idx: usize, col_idx: usize) -> Option<usize> {
+    if grid[row_idx][col_idx] != Item::Roll {
+        return None;
+    }
+
+    let is_valid = |r: isize, c: isize| -> bool {
+        r >= 0 && (r as usize) < grid.len() && c >= 0 && (c as usize) < grid[0].len()
+    };
+
+    let count = DIRECTIONS.iter().filter(|d| {
+        let new_pos = (row_idx as isize + d.0, col_idx as isize + d.1);
+
+        let valid = is_valid(new_pos.0, new_pos.1) && (grid[new_pos.0 as usize][new_pos.1 as usize] == Item::Roll);
+        valid
+    }).count();
+
+    Some(count)
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let rows = input.split('\n').filter(|l| !l.is_empty()).collect_vec();
+    let row_count = rows.len() as usize;
+    let col_count = rows[0].len() as usize;
+    let grid = rows.into_iter().map(|r| r.chars().map(|c| match c {
+        '.' => Item::Empty,
+        '@' => Item::Roll,
+        _ => panic!("Unknown character"),
+    }).collect_vec()).collect_vec();
+    // println!("Rows: {row_count}, Cols: {col_count}");
+
+    let mut total_rolls: u64 = 0;
+    for r in 0..row_count {
+        for c in 0..col_count {
+            if grid[r][c] != Item::Roll {
+                continue;
+            }
+
+            let rolls = roll_count(&grid, r, c).unwrap();
+            if rolls < 4 {
+                total_rolls += 1;
+                // println!("{} rolls@({}, {})", rolls, r, c);
+            }
+        }
+    }
+    Some(total_rolls)
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let rows = input.split('\n').filter(|l| !l.is_empty()).collect_vec();
+    let row_count = rows.len() as usize;
+    let col_count = rows[0].len() as usize;
+    let mut grid = rows.into_iter().map(|r| r.chars().map(|c| match c {
+        '.' => Item::Empty,
+        '@' => Item::Roll,
+        _ => panic!("Unknown character"),
+    }).collect_vec()).collect_vec();
+
+    let mut total_rolls_removed = 0;
+    loop {
+        let mut rolls_removed = 0;
+        for r in 0..row_count {
+            for c in 0..col_count {
+                if grid[r][c] != Item::Roll {
+                    continue;
+                }
+
+                let rolls = roll_count(&grid, r, c).unwrap();
+                if rolls < 4 {
+                    grid[r][c] = Item::Empty;
+                    rolls_removed += 1;
+                    // println!("{} rolls@({}, {})", rolls, r, c);
+                }
+            }
+        }
+
+        total_rolls_removed += rolls_removed;
+        // println!("Rolls removed this round: {} (total: {})", rolls_removed, total_rolls_removed);
+        if rolls_removed == 0 {
+            break;
+        }
+    }
+
+    Some(total_rolls_removed)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(13)); // 2484 too high
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(43));
+    }
+}