Day 9 complete

2022/rust/src/day9.rs

@@ -57,7 +57,48 @@ fn part1(input: &Input) -> Answer {
 }
 
 fn part2(input: &Input) -> Answer {
-    0
+    let mut p: HashSet<(i32, i32)> = HashSet::new();
+    let mut r: Vec<(i32, i32)> = std::iter::repeat((0, 0)).take(10).collect();
+
+    let mut m = |x, y, n| {
+        for _ in 0..n {
+            r[0].0 += x;
+            r[0].1 += y;
+            for s in 1..r.len() {
+                if r[s].0.abs_diff(r[s - 1].0) > 1 && r[s].1.abs_diff(r[s - 1].1) > 1 {
+                    r[s].0 += (r[s - 1].0 - r[s].0) / 2;
+                    r[s].1 += (r[s - 1].1 - r[s].1) / 2;
+                } else if r[s].0.abs_diff(r[s - 1].0) > 1 {
+                    r[s].0 += (r[s - 1].0 - r[s].0) / 2;
+                    r[s].1 = r[s - 1].1;
+                } else if r[s].1.abs_diff(r[s - 1].1) > 1 {
+                    r[s].1 += (r[s - 1].1 - r[s].1) / 2;
+                    r[s].0 = r[s - 1].0;
+                }
+            }
+            p.insert(r[r.len() - 1]);
+            println!(
+                "h: ({}, {}), t: ({}, {})",
+                r[0].0,
+                r[0].1,
+                r[r.len() - 1].0,
+                r[r.len() - 1].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 main() {
@@ -84,6 +125,21 @@ R 2";
     fn test() {
         let input = processed_input(TEST_INPUT);
         assert_eq!(part1(&input), 13);
-        assert_eq!(part2(&input), 0);
+        assert_eq!(part2(&input), 1);
+    }
+
+    const TEST_INPUT2: &str = "R 5
+U 8
+L 8
+D 3
+R 17
+D 10
+L 25
+U 20";
+
+    #[test]
+    fn part2_test2() {
+        let input2 = processed_input(TEST_INPUT2);
+        assert_eq!(part2(&input2), 36);
     }
 }