Day 10

diff --git a/src/day10.rs b/src/day10.rs
new file mode 100644 (file)
index 0000000..27bb5ab
--- /dev/null
+++ b/src/day10.rs
@@ -0,0 +1,249 @@
+pub enum Instruction {
+    Noop,
+    Addx(i32),
+}
+
+pub fn parse(input: &str) -> Vec<Instruction> {
+    input.lines().map(|l| {
+        let split: Vec<&str> = l.trim().split(' ').collect();
+        match split[0] {
+            "noop" => Instruction::Noop,
+            "addx" => Instruction::Addx(split[1].parse::<i32>().unwrap()),
+            other => panic!("Unknown instruction: {}", other),
+        }
+    }).collect()
+}
+
+pub struct Screen {
+    screen: Vec<Vec<bool>>,
+}
+
+impl Screen {
+    pub fn new() -> Self {
+        Screen { screen: Vec::new() }
+    }
+
+    pub fn draw_screen(&mut self, instructions: &[Instruction]) -> i32 {
+        let mut x = 1; // Middle sprite position, sprite is 3 pixels wide.
+        let mut signal_strength = 0;
+        let mut cycle = 0;
+
+        let mut tick = |x: &i32| {
+            let pos_x = cycle % 40;
+            let pos_y = cycle / 40;
+            if pos_x == 0 {
+                self.screen.push(vec![false; 40])
+            }
+
+            if pos_x >= x - 1 && pos_x <= x + 1 {
+                self.screen[pos_y as usize][pos_x as usize] = true;
+            }
+
+            cycle += 1;
+
+            if (cycle - 20) % 40 == 0 {
+                signal_strength += x * cycle;
+            }
+
+        };
+
+        for i in instructions {
+            match i {
+                Instruction::Noop => tick(&x),
+                Instruction::Addx(v) => {
+                    tick(&x);
+                    tick(&x);
+                    x += *v;
+                }
+            }
+        }
+
+        signal_strength
+    }
+
+    pub fn to_ascii(&self) -> String {
+        let mut ascii = String::new();
+        for line in self.screen.iter() {
+            ascii += &line.iter().map(|p| if *p { '#' } else { '.' }).collect::<String>();
+            ascii += "\n";
+        }
+        ascii
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    static INSTRUCTION: &str =
+        "addx 15
+         addx -11
+         addx 6
+         addx -3
+         addx 5
+         addx -1
+         addx -8
+         addx 13
+         addx 4
+         noop
+         addx -1
+         addx 5
+         addx -1
+         addx 5
+         addx -1
+         addx 5
+         addx -1
+         addx 5
+         addx -1
+         addx -35
+         addx 1
+         addx 24
+         addx -19
+         addx 1
+         addx 16
+         addx -11
+         noop
+         noop
+         addx 21
+         addx -15
+         noop
+         noop
+         addx -3
+         addx 9
+         addx 1
+         addx -3
+         addx 8
+         addx 1
+         addx 5
+         noop
+         noop
+         noop
+         noop
+         noop
+         addx -36
+         noop
+         addx 1
+         addx 7
+         noop
+         noop
+         noop
+         addx 2
+         addx 6
+         noop
+         noop
+         noop
+         noop
+         noop
+         addx 1
+         noop
+         noop
+         addx 7
+         addx 1
+         noop
+         addx -13
+         addx 13
+         addx 7
+         noop
+         addx 1
+         addx -33
+         noop
+         noop
+         noop
+         addx 2
+         noop
+         noop
+         noop
+         addx 8
+         noop
+         addx -1
+         addx 2
+         addx 1
+         noop
+         addx 17
+         addx -9
+         addx 1
+         addx 1
+         addx -3
+         addx 11
+         noop
+         noop
+         addx 1
+         noop
+         addx 1
+         noop
+         noop
+         addx -13
+         addx -19
+         addx 1
+         addx 3
+         addx 26
+         addx -30
+         addx 12
+         addx -1
+         addx 3
+         addx 1
+         noop
+         noop
+         noop
+         addx -9
+         addx 18
+         addx 1
+         addx 2
+         noop
+         noop
+         addx 9
+         noop
+         noop
+         noop
+         addx -1
+         addx 2
+         addx -37
+         addx 1
+         addx 3
+         noop
+         addx 15
+         addx -21
+         addx 22
+         addx -6
+         addx 1
+         noop
+         addx 2
+         addx 1
+         noop
+         addx -10
+         noop
+         noop
+         addx 20
+         addx 1
+         addx 2
+         addx 2
+         addx -6
+         addx -11
+         noop
+         noop
+         noop";
+
+    #[test]
+    fn part1() {
+        let instructions = parse(INSTRUCTION);
+        let mut screen = Screen::new();
+        assert_eq!(screen.draw_screen(&instructions), 13140);
+    }
+
+    #[test]
+    fn part2() {
+        let instructions = parse(INSTRUCTION);
+        let mut screen = Screen::new();
+        screen.draw_screen(&instructions);
+        println!("{}", screen.to_ascii());
+
+        assert_eq!(screen.to_ascii(),
+    "##..##..##..##..##..##..##..##..##..##..
+###...###...###...###...###...###...###.
+####....####....####....####....####....
+#####.....#####.....#####.....#####.....
+######......######......######......####
+#######.......#######.......#######.....
+");
+    }
+}
\ No newline at end of file

diff --git a/src/main.rs b/src/main.rs
index 44cbcd1..d7d6d19 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -10,6 +10,7 @@ mod day06;
 mod day07;
 mod day08;
 mod day09;
+mod day10;
 
 fn day01() -> String {
     let f = fs::File::open("data/day01.input").unwrap();
@@ -76,6 +77,13 @@ fn day09() -> String {
     format!("part1: {}, part2: {}", day09::nb_positions_visited_by_tail::<2>(&movements), day09::nb_positions_visited_by_tail::<10>(&movements))
 }
 
+fn day10() -> String {
+    let instructions = day10::parse(&fs::read_to_string("data/day10.input").unwrap());
+    let mut screen = day10::Screen::new();
+    let sum_signal_strength = screen.draw_screen(&instructions);
+    format!("part1: {}, part2: \n{}", sum_signal_strength, screen.to_ascii())
+}
+
 fn format_micros(t: u128) -> String {
     if t < 10_000 {
         format!("{} μs", t)
@@ -104,6 +112,7 @@ fn main() {
         day07,
         day08,
         day09,
+        day10,
     );
 
     let args: Vec<String> = env::args().skip(1).collect();