Solutions to day 08. ★

2016/day-08/src/main.rs

@@ -0,0 +1,88 @@
+use std::env;
+use std::io::prelude::*;
+use std::io::BufReader;
+use std::fs::File;
+
+fn is_splitpoint(c: char) -> bool
+{
+    match c {
+        ' ' => true,
+        'x' => true,
+        'y' => true,
+        '=' => true,
+        _ => false,
+    }
+}
+
+const WIDTH: usize = 50;
+const HEIGHT: usize = 6;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    let f = File::open(&args[1]).expect("Could not open file");
+    let reader = BufReader::new(f);
+
+    let mut lights = [[false; HEIGHT]; WIDTH];
+    for line in reader.lines() {
+        let contents = line.unwrap();
+        let parts: Vec<&str> = contents.split(|c| is_splitpoint(c)).collect();
+
+        match parts[0] {
+            "rect" => {
+                let width: usize = parts[1].parse().unwrap();
+                let height: usize = parts[2].parse().unwrap();
+                for x in 0..width {
+                    for y in 0..height {
+                        lights[x][y] = true;
+                    }
+                }
+            },
+            "rotate" => {
+                let index: usize = parts[4].parse().expect("Invalid index");
+                let amount: usize = parts[7].parse().expect("Invalid row");
+                match parts[1] {
+                    "row" => {
+                        let mut copy = [false; WIDTH];
+                        for x in 0..WIDTH {
+                            copy[x] = lights[x][index];
+                        }
+                        for x in 0..WIDTH {
+                            lights[(x + amount) % WIDTH][index] = copy[x];
+                        }
+                    },
+                    "column" => {
+                        let mut copy = [false; HEIGHT];
+                        for y in 0..HEIGHT {
+                            copy[y] = lights[index][y];
+                        }
+                        for y in 0..HEIGHT {
+                            lights[index][(y + amount) % HEIGHT] = copy[y];
+                        }
+                    }
+                    _ => panic!("{} is not a supported rotation", parts[1]),
+                }
+            },
+            _ => panic!("{} is not a supported operation", parts[0]),
+        }
+    }
+
+    let mut count = 0;
+    for y in 0..HEIGHT {
+        for x in 0..WIDTH {
+            let mut c = ' ';
+            if lights[x][y] {
+                count += 1;
+                c = '★';
+            }
+            print!("{}", c);
+
+            // spacing between letters
+            if x % 5 == 4 {
+                print!(" ");
+            }
+        }
+        println!("");
+    }
+
+    println!("{} lights active.", count);
+}