day 8 (part 2)

1 files changed, 72 insertions, 0 deletions

diff --git a/src/day-8/part-2.zig b/src/day-8/part-2.zig
new file mode 100644
index 0000000..9f7a22b
--- /dev/null
+++ b/src/day-8/part-2.zig
@@ -0,0 +1,72 @@
+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;
+        }
+
+    }
+
+}