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
57
|
use std::io::{self, Read};
// 17 16 15 14 13
// 18 5 4 3 12
// 19 6 1 2 11
// 20 7 8 9 10
// 21 22 23---> ...
//
// 1 R
// 1 U
// 2 L
// 2 D
// 3 R
// 3 U
// 4 L
// 4 D
// 5 R
fn solve1(input: i32) -> i32 {
let ds = [(1, 0), (0, 1), (-1, 0), (0, -1)];
let mut n = 1;
let mut x = 0i32;
let mut y = 0i32;
let mut r = 1;
let mut i = 0;
for &(dx, dy) in ds.iter().cycle() {
for _ in 0..r {
if n == input {
return x.abs() + y.abs();
}
n += 1;
x += dx;
y += dy;
}
r += i % 2;
i += 1;
}
unreachable!()
}
fn main() {
let mut input = String::new();
io::stdin().read_to_string(&mut input).unwrap();
println!("Part 1: {}", solve1(input.trim().parse().unwrap()));
}
#[test]
fn part1() {
assert_eq!(0, solve1(1));
assert_eq!(3, solve1(12));
assert_eq!(2, solve1(23));
assert_eq!(31, solve1(1024));
}
|