Add 2022/09/1

2022/src/bin/day09.rs

@@ -0,0 +1,71 @@
+#![feature(test)]
+extern crate test;
+use std::collections::HashSet;
+
+use aoc2022::{boilerplate, common::*};
+
+const DAY: usize = 9;
+type Parsed = Vec<(u8, usize)>;
+
+fn parse_input(raw: &str) -> Parsed {
+    raw.lines().map(|l| (l.as_bytes()[0], parse_num(&l[2..]))).collect()
+}
+
+fn part1(parsed: &Parsed) -> usize {
+    let mut positions = HashSet::from([(0, 0)]);
+    let mut head = (0, 0);
+    let mut tail = (0, 0);
+    for &(dir, n) in parsed {
+        for _ in 0..n {
+            match dir {
+                b'U' => head.1 += 1,
+                b'D' => head.1 -= 1,
+                b'L' => head.0 -= 1,
+                b'R' => head.0 += 1,
+                _ => unreachable!(),
+            }
+            if step_towards(&mut tail, &head) {
+                positions.insert(tail);
+            }
+        }
+    }
+    positions.len()
+}
+
+fn step_towards(tail: &mut (i32, i32), head: &(i32, i32)) -> bool {
+    let xdiff = head.0 - tail.0;
+    let ydiff = head.1 - tail.1;
+    match (xdiff.abs(), ydiff.abs()) {
+        (0 | 1, 0 | 1) => return false,
+        (_, 0) => tail.0 += xdiff.signum(),
+        (0, _) => tail.1 += ydiff.signum(),
+        (1, _) | (_, 1) => {
+            tail.0 += xdiff.signum();
+            tail.1 += ydiff.signum();
+        }
+        _ => return false,
+    }
+    true
+}
+
+fn part2(parsed: &Parsed) -> usize {
+    unimplemented!()
+}
+
+boilerplate! {
+    TEST_INPUT == "R 4
+U 4
+L 3
+D 1
+R 4
+D 1
+L 5
+R 2",
+    tests: {
+        part1: { TEST_INPUT => 13 },
+        part2: { TEST_INPUT => 0 },
+    },
+    bench1 == 6367,
+    bench2 == 0,
+    bench_parse: Vec::len => 2000,
+}