2018/src/day6.rs


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

use std::io;
use std::io::BufRead;

const W: i32 = 800;

fn dist(a: (i32, i32), b: (i32, i32)) -> i32 {
    (b.0 - a.0).abs() + (b.1 - a.1).abs()
}

pub fn main<T: BufRead>(reader: T) -> io::Result<(String, String)> {
    let pts: Vec<(i32, i32)> = reader.lines().map(|l| l.unwrap()).map(|line| {
        let mut spl = line.split(", ").map(|s| s.parse().unwrap());
        let x = spl.next().unwrap();
        let y = spl.next().unwrap();
        (x, y)
    }).collect();

    let mut borderpts = vec![false; pts.len()];
    let mut size = vec![0; pts.len()];
    let mut nsafe = 0;

    for y in -W..W+1 {
        for x in -W..W+1 {
            let closest = (0..pts.len()).min_by_key(|&i| dist(pts[i], (x, y))).unwrap();
            if x == -W || x == W || y == -W || y == W {
                borderpts[closest] = true;
            } else {
                size[closest] += 1;
            }

            let distsum: i32 = pts.iter().map(|&p| dist(p, (x, y))).sum();
            if distsum < 10000 {
                nsafe += 1;
            }
        }
    }

    let part1 = size[(0..pts.len()).max_by_key(|&i| if borderpts[i] { -1 } else { size[i] }).unwrap()].to_string();
    let part2 = nsafe.to_string();

    Ok((part1, part2))
}