aoc; day 2021.25

advent-of-code/2021/day25/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day25"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

advent-of-code/2021/day25/src/main.rs

@@ -0,0 +1,55 @@
+use std::fs;
+
+fn main() {
+    let mut map: Vec<Vec<u8>> = fs::read_to_string("../inputs/25")
+        .unwrap()
+        .lines()
+        .map(|line| line.bytes().collect())
+        .collect();
+
+    let mut steps = 0;
+    let h = map.len();
+    let w = map[0].len();
+
+    loop {
+        steps += 1;
+
+        let mut horizontal = vec![];
+
+        for x in 0..h {
+            for y in 0..w {
+                let adjancent = (y + 1) % w;
+                if map[x][y] == b'>' && map[x][adjancent] == b'.' {
+                    horizontal.push((x, y, adjancent));
+                }
+            }
+        }
+
+        for &(x, y, a) in &horizontal {
+            map[x][y] = b'.';
+            map[x][a] = b'>';
+        }
+
+        let mut vertical = vec![];
+
+        for x in 0..h {
+            for y in 0..w {
+                let adjancent = (x + 1) % h;
+                if map[x][y] == b'v' && map[adjancent][y] == b'.' {
+                    vertical.push((x, y, adjancent));
+                }
+            }
+        }
+
+        for &(x, y, a) in &vertical {
+            map[x][y] = b'.';
+            map[a][y] = b'v';
+        }
+
+        if vertical.is_empty() && horizontal.is_empty() {
+            break;
+        }
+    }
+
+    println!("final = {}", steps);
+}