d18

day18/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day17"
+version = "0.1.0"

day18/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day17"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

day18/src/main.rs

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+use std::io;
+use std::env;
+use std::fs::File;
+use std::io::BufReader;
+use std::io::BufRead;
+use std::collections::HashSet;
+
+
+fn main() -> io::Result<()> {
+    let input_fname = env::args().nth(1).expect("need input file");
+    let lines = BufReader::new(File::open(input_fname)?).lines();
+    let mut cubes: HashSet<(i8, i8, i8)> = HashSet::new();
+
+    for line in lines.flatten() {
+        let mut split = line.split(',');
+        let x = split.next().unwrap().to_string().parse::<i8>().unwrap();
+        let y = split.next().unwrap().to_string().parse::<i8>().unwrap();
+        let z = split.next().unwrap().to_string().parse::<i8>().unwrap();
+        cubes.insert((x, y, z));
+    }
+
+    let mut all_neighbors = 0;
+    for (x, y, z) in &cubes {
+        let neighbors = HashSet::from([
+            (*x + 1, *y, *z), (*x - 1, *y, *z),
+            (*x, *y + 1, *z), (*x, *y - 1, *z),
+            (*x, *y, *z + 1), (*x, *y, *z - 1)
+        ]);
+        all_neighbors += cubes.intersection(&neighbors).count();
+    }
+    println!("{}", cubes.len() * 6 - all_neighbors);
+    Ok(())
+}
+

day18/test.txt

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+2,2,2
+1,2,2
+3,2,2
+2,1,2
+2,3,2
+2,2,1
+2,2,3
+2,2,4
+2,2,6
+1,2,5
+3,2,5
+2,1,5
+2,3,5