d6p1

2024/day06/src/lib.rs

@@ -0,0 +1,95 @@
+use helper::{Day, Variants};
+
+pub fn main() {
+    helper::main::<Day06>(include_str!("../input.txt"));
+}
+
+struct Day06;
+
+helper::define_variants! {
+    day => crate::Day06;
+    part1 {
+        basic => crate::part1;
+    }
+    part2 {
+        basic => crate::part2;
+    }
+}
+
+impl Day for Day06 {
+    fn part1() -> Variants {
+        part1_variants!(construct_variants)
+    }
+
+    fn part2() -> Variants {
+        part2_variants!(construct_variants)
+    }
+}
+
+fn part1(input: &str) -> u64 {
+    let input = input.as_bytes();
+
+    let width = input.iter().position(|&byte| byte == b'\n').unwrap() + 1; // account for newline
+    let mut guard_pos = input
+        .iter()
+        .position(|&byte| byte == b'^' || byte == b'>' || byte == b'<' || byte == b'v')
+        .unwrap();
+    let mut guard_state = input[guard_pos];
+
+    let mut reached_tiles = vec![false; input.len()];
+    reached_tiles[guard_pos] = true;
+
+    loop {
+        let new_pos = match guard_state {
+            b'^' => guard_pos.checked_sub(width),
+            b'v' => guard_pos.checked_add(width),
+            b'<' => guard_pos.checked_sub(1),
+            b'>' => guard_pos.checked_add(1),
+            _ => unreachable!(),
+        };
+        match new_pos {
+            None => {
+                break;
+            }
+            Some(new_pos) if input.len() <= new_pos => {
+                break;
+            }
+            Some(new_pos) if input[new_pos] == b'\n' => {
+                break;
+            }
+            Some(new_pos) => {
+                if input[new_pos] == b'#' {
+                    guard_state = match guard_state {
+                        b'^' => b'>',
+                        b'v' => b'<',
+                        b'<' => b'^',
+                        b'>' => b'v',
+                        _ => unreachable!(),
+                    }
+                } else {
+                    reached_tiles[new_pos] = true;
+                    guard_pos = new_pos;
+                }
+            }
+        }
+    }
+
+    reached_tiles.iter().filter(|reached| **reached).count() as u64
+}
+
+fn part2(_input: &str) -> u64 {
+    0
+}
+
+helper::tests! {
+    day06 Day06;
+    part1 {
+        small => 41;
+        default => 4454;
+    }
+    part2 {
+        small => 0;
+        default => 0;
+    }
+}
+helper::benchmarks! {}

2024/day06/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    day06::main();
+}