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
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
|
const std = @import("std");
const point = struct { x: i64, y: i64, z: i64 };
const dist = struct { dist: f64, a: usize, b: usize };
pub fn distance(a: point, b: point) f64 {
const x = std.math.pow(i64, a.x - b.x, 2);
const y = std.math.pow(i64, a.y - b.y, 2);
const z = std.math.pow(i64, a.z - b.z, 2);
return @abs(@sqrt(@as(f64, @floatFromInt(x + y + z))));
}
pub fn asc_dist(_: void, a: dist, b:dist) bool {
return a.dist < b.dist;
}
pub fn main() !void {
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
defer _ = gpa.deinit();
const alloc = gpa.allocator();
const path = "input.txt";
const fp = try std.fs.cwd().openFile(path, .{.mode = std.fs.File.OpenMode.read_only});
defer fp.close();
var reader = fp.reader();
var buffer: [256]u8 = undefined;
var points = std.ArrayList(point).init(alloc);
defer points.deinit();
while(try reader.readUntilDelimiterOrEof(&buffer, '\n')) |line| {
const v1 = std.mem.indexOf(u8, line, ",").?;
const v2 = std.mem.indexOf(u8, line[v1+1..], ",").? + v1+1;
const p = point{
.x = try std.fmt.parseInt(i64, line[0..v1], 10),
.y = try std.fmt.parseInt(i64, line[v1+1..v2], 10),
.z = try std.fmt.parseInt(i64, line[v2+1..], 10),
};
try points.append(p);
}
var dists = std.ArrayList(dist).init(alloc);
defer dists.deinit();
var used = std.AutoHashMap(usize, bool).init(alloc);
defer used.deinit();
for(0..points.items.len) |a| {
for(a..points.items.len) |b| {
if(a == b) continue;
const d = distance(points.items[a], points.items[b]);
try dists.append(dist{.dist = d, .a = a, .b = b});
}
}
std.mem.sort(dist, dists.items, {}, asc_dist);
for(dists.items) |o| {
try used.put(o.a, true);
try used.put(o.b, true);
if(used.count() >= points.items.len) {
std.debug.print("{}\n", .{points.items[o.a].x * points.items[o.b].x});
break;
}
}
}
|
