1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
use core::panic;
use std::collections::HashSet;
type Pt = (i32, i32);
/**
* how should the tail move to catch up with the head?
*/
fn catchup(head: Pt, tail: Pt) -> Pt {
let (hx, hy) = head;
let (tx, ty) = tail;
let xdiff = hx - tx;
let ydiff = hy - ty;
// only move if we're not adjescent (incl diagonally)
if xdiff.abs() > 1 || ydiff.abs() > 1 {
// only move 1 square (x and or y) in the direction of the head
(tail.0 + xdiff.signum(), tail.1 + ydiff.signum())
} else {
(tail.0, tail.1)
}
}
pub fn run(input: String) {
// series of steps
// let mut head: Pt = (0,0);
// let mut tail: Pt = (0,0);
// let mut htrail: Vec<Pt> = Vec::new();
let mut rope: Vec<Pt> = (0..10).map(|_| { (0,0) as Pt}).collect();
let mut trail: Vec<Pt> = Vec::new();
for line in input.lines() {
let mut toks = line.split_whitespace();
let dir: &str = toks.next().expect("expected a direction!");
let reps: u32 = toks.next().expect("expected a reps!").parse().expect("reps wasn't a number!");
for _ in 0..reps {
let head = rope[0];
let newhead = match dir {
"U" => (head.0, head.1+1),
"D" => (head.0, head.1-1),
"L" => (head.0-1, head.1),
"R" => (head.0+1, head.1),
dir => panic!("unexpected direction {}", dir),
};
rope[0] = newhead;
for l in 1..rope.len() {
rope[l] = catchup(rope[l-1], rope[l]);
}
let tail = rope.last().unwrap();
// htrail.push(head);
// tail = catchup(head, tail);
trail.push(*tail);
}
}
//println!("htrail {:?}", htrail);
//println!("trail {:?}", trail);
let trailsz = trail.into_iter().collect::<HashSet<Pt>>().len();
println!("Day 9: {}", trailsz);
}
|
