Year 2025 Day 6

Author: maneatingape

README.md

@@ -82,6 +82,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | 3 | [Lobby](https://adventofcode.com/2025/day/3) | [Source](src/year2025/day03.rs) | 21 |
 | 4 | [Printing Department](https://adventofcode.com/2025/day/4) | [Source](src/year2025/day04.rs) | 177 |
 | 5 | [Cafeteria](https://adventofcode.com/2025/day/5) | [Source](src/year2025/day05.rs) | 20 |
+| 6 | [Trash Compactor](https://adventofcode.com/2025/day/6) | [Source](src/year2025/day06.rs) | 20 |
 
 ## 2024
 

benches/benchmark.rs

@@ -95,5 +95,5 @@ benchmark!(year2024
 );
 
 benchmark!(year2025
-    day01, day02, day03, day04, day05
+    day01, day02, day03, day04, day05, day06
 );

src/lib.rs

@@ -74,5 +74,5 @@ library!(year2024 "Locate the Chief Historian in time for the big Christmas slei
 );
 
 library!(year2025 "Finish the North Pole decorations in time for Christmas."
-    day01, day02, day03, day04, day05
+    day01, day02, day03, day04, day05, day06
 );

src/main.rs

@@ -141,5 +141,5 @@ run!(year2024
 );
 
 run!(year2025
-    day01, day02, day03, day04, day05
+    day01, day02, day03, day04, day05, day06
 );

src/year2025/day06.rs

@@ -0,0 +1,39 @@
+//! # Trash Compactor
+use crate::util::grid::*;
+use crate::util::point::*;
+
+type Input = (u64, u64);
+
+pub fn parse(input: &str) -> Input {
+    let grid = Grid::parse(input);
+    let bottom = grid.height - 1;
+    let mut right = grid.width;
+
+    (0..grid.width).rev().filter(|&x| grid[Point::new(x, bottom)] != b' ').fold(
+        (0, 0),
+        |(part_one, part_two), left| {
+            let rows = (0..bottom).map(|y| (left..right).fold(0, |num, x| acc(&grid, num, x, y)));
+            let cols = (left..right).map(|x| (0..bottom).fold(0, |num, y| acc(&grid, num, x, y)));
+
+            let plus = grid[Point::new(left, bottom)] == b'+';
+            let first: u64 = if plus { rows.sum() } else { rows.product() };
+            let second: u64 = if plus { cols.sum() } else { cols.product() };
+
+            right = left - 1;
+            (part_one + first, part_two + second)
+        },
+    )
+}
+
+pub fn part1(input: &Input) -> u64 {
+    input.0
+}
+
+pub fn part2(input: &Input) -> u64 {
+    input.1
+}
+
+fn acc(grid: &Grid<u8>, number: u64, x: i32, y: i32) -> u64 {
+    let digit = grid[Point::new(x, y)];
+    if digit == b' ' { number } else { 10 * number + u64::from(digit - b'0') }
+}

tests/test.rs

@@ -87,5 +87,5 @@ test!(year2024
 );
 
 test!(year2025
-    day01, day02, day03, day04, day05
+    day01, day02, day03, day04, day05, day06
 );

tests/year2025/day06.rs

@@ -0,0 +1,19 @@
+use aoc::year2025::day06::*;
+
+const EXAMPLE: &str = "\
+123 328  51 64 
+ 45 64  387 23 
+  6 98  215 314
+*   +   *   +  ";
+
+#[test]
+fn part1_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part1(&input), 4277556);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part2(&input), 3263827);
+}