day 10

src/days/day10.rs

@@ -0,0 +1,103 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+
+#[derive(Debug, Clone, Copy)]
+enum Instruction {
+    AddX(i32),
+    NoOp,
+}
+
+#[aoc_generator(day10)]
+fn generator(input: &str) -> Vec<Instruction> {
+    input
+        .lines()
+        .map(|l| {
+            if l == "noop" {
+                Instruction::NoOp
+            } else if let Some(l) = l.strip_prefix("addx ") {
+                Instruction::AddX(l.parse().unwrap())
+            } else {
+                panic!()
+            }
+        })
+        .collect()
+}
+
+struct CpuState {
+    cycle: i32,
+    x: i32,
+}
+
+fn run_simulation(input: &[Instruction], mut during_cycle_handler: impl FnMut(CpuState)) {
+    let mut cycle = 1;
+    let mut x = 1;
+    let mut iter = input.iter().copied();
+    let mut current_instruction = iter.next().unwrap();
+    let mut current_instruction_cycle = 0;
+
+    // god i hate fenceposts
+    loop {
+        // START OF CYCLE
+
+        let need_new_instruction = match (current_instruction, current_instruction_cycle) {
+            (_, 0) => false,
+            (Instruction::NoOp, 1) => true,
+            (Instruction::AddX(_), 1) => false,
+            (Instruction::AddX(v), 2) => {
+                x += v;
+                true
+            }
+            _ => unreachable!(),
+        };
+
+        if need_new_instruction {
+            let Some(tmp) = iter.next() else {
+                break
+            };
+            current_instruction = tmp;
+            current_instruction_cycle = 0;
+        }
+
+        // DURING CYCLE
+
+        during_cycle_handler(CpuState { cycle, x });
+
+        // END OF CYCLE
+
+        current_instruction_cycle += 1;
+        cycle += 1;
+    }
+}
+
+#[aoc(day10, part1)]
+fn part1(input: &[Instruction]) -> i32 {
+    let mut res = 0;
+
+    run_simulation(input, |CpuState { cycle, x }| {
+        if (cycle + 20) % 40 == 0 {
+            res += cycle * x;
+        }
+    });
+
+    res
+}
+
+#[aoc(day10, part2)]
+fn part2(input: &[Instruction]) -> String {
+    let mut res = "\n".to_owned(); // newline so that `cargo aoc` formats this nicely
+
+    run_simulation(input, |CpuState { cycle, x }| {
+        let crt_x_pos = (cycle - 1) % 40;
+
+        if (crt_x_pos - x).abs() <= 1 {
+            res.push('#');
+        } else {
+            res.push(' '); // the puzzle says `.` but ` ` is more readable
+        }
+
+        if cycle % 40 == 0 {
+            res.push('\n');
+        }
+    });
+
+    res
+}

src/lib.rs

@@ -10,6 +10,8 @@ mod days {
     mod day7;
     mod day8;
     mod day9;
+    // curse you, rustfmt
+    mod day10;
 }
 
 aoc_lib! { year = 2022 }