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) | 28 |
 
 ## 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 +1,51 @@
+use crate::util::grid::*;
+use crate::util::parse::*;
+use crate::util::point::*;
+
+pub fn parse(input: &str) -> &str {
+    input
+}
+
+pub fn part1(input: &str) -> u64 {
+    let lines: Vec<_> = input.lines().rev().collect();
+    let mut rows: Vec<_> = lines[1..].iter().map(|line| line.iter_unsigned::<u64>()).collect();
+
+    lines[0]
+        .split_ascii_whitespace()
+        .map(|operation| {
+            let column = rows.iter_mut().filter_map(Iterator::next);
+            if operation == "+" { column.sum::<u64>() } else { column.product::<u64>() }
+        })
+        .sum()
+}
+
+pub fn part2(input: &str) -> u64 {
+    let grid = Grid::parse(input);
+    let top = grid.height - 1;
+
+    let mut total = 0;
+    let mut start = 0;
+
+    while start < grid.width {
+        let mut end = start + 1;
+        while end < grid.width && grid[Point::new(end, top)] == b' ' {
+            end += 1;
+        }
+        if end < grid.width {
+            end -= 1;
+        }
+
+        let column = (start..end).map(|x| {
+            (0..top).fold(0, |number, y| {
+                let digit = grid[Point::new(x, y)];
+                if digit == b' ' { number } else { 10 * number + (digit - b'0') as u64 }
+            })
+        });
+
+        let plus = grid[Point::new(start, top)] == b'+';
+        total += if plus { column.sum::<u64>() } else { column.product::<u64>() };
+        start = end + 1;
+    }
+
+    total
+}

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);
+}