Part 1

2022/rust/Cargo.toml

@@ -46,4 +46,8 @@ path = "src/day7.rs"
 name = "day8"
 path = "src/day8.rs"
 
+[[bin]]
+name = "day9"
+path = "src/day9.rs"
+
 [dependencies]

2022/rust/src/day9.rs

@@ -0,0 +1,89 @@
+mod common;
+
+use std::collections::HashSet;
+
+type Input = Vec<(char, i32)>;
+type Answer = usize;
+
+fn processed_input(input: &str) -> Input {
+    input
+        .lines()
+        .map(|l| {
+            let mut args = l.split(' ');
+            (
+                args.next().unwrap().chars().next().unwrap(),
+                args.next().unwrap().parse::<i32>().unwrap(),
+            )
+        })
+        .collect()
+}
+
+fn part1(input: &Input) -> Answer {
+    let mut p: HashSet<(i32, i32)> = HashSet::new();
+    let mut h: (i32, i32) = (0, 0);
+    let mut t: (i32, i32) = (0, 0);
+
+    let mut m = |x, y, n| {
+        for _ in 0..n {
+            h.0 += x;
+            h.1 += y;
+            if t.0.abs_diff(h.0) > 1 && t.1.abs_diff(h.1) > 1 {
+                t.0 += (h.0 - t.0) / 2;
+                t.1 += (h.1 - t.1) / 2;
+            } else if t.0.abs_diff(h.0) > 1 {
+                t.0 += (h.0 - t.0) / 2;
+                t.1 = h.1;
+            } else if t.1.abs_diff(h.1) > 1 {
+                t.1 += (h.1 - t.1) / 2;
+                t.0 = h.0;
+            }
+            p.insert(t);
+            println!("h: ({}, {}), t: ({}, {})", h.0, h.1, t.0, t.1);
+        }
+    };
+
+    for i in input {
+        println!("{:?}", i);
+        match i.0 {
+            'L' => m(-1, 0, i.1),
+            'R' => m(1, 0, i.1),
+            'U' => m(0, -1, i.1),
+            'D' => m(0, 1, i.1),
+            _ => (),
+        }
+    }
+
+    p.len()
+}
+
+fn part2(input: &Input) -> Answer {
+    0
+}
+
+fn main() {
+    let input_text = common::day_input(9);
+    eprintln!("{}\n\nAbove is your input file.\n\n", input_text);
+    let input = processed_input(&input_text);
+    common::show_answers(&part1(&input), &part2(&input))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TEST_INPUT: &str = "R 4
+U 4
+L 3
+D 1
+R 4
+D 1
+L 5
+R 2";
+
+    #[test]
+    fn test() {
+        let input = processed_input(TEST_INPUT);
+        assert_eq!(part1(&input), 13);
+        assert_eq!(part2(&input), 0);
+    }
+}