const std = @import("std"); var printBuffer: [1024]u8 = undefined; var allocatorBuffer: [100*1024*1024]u8 = undefined; const Junction = struct { x: i64 = 0, y: i64 = 0, z: i64 = 0, }; const JunctionPair = struct { a: usize = 0, b: usize = 0, pub fn distanceSquared(self: JunctionPair, junctions: []Junction) i64 { const ja = &junctions[self.a]; const jb = &junctions[self.b]; const dx = ja.x - jb.x; const dy = ja.y - jb.y; const dz = ja.z - jb.z; return dx * dx + dy * dy + dz * dz; } }; const JunctionIdNode = struct { id: usize = 0, node: std.DoublyLinkedList.Node = .{}, }; const Circuit = struct { junctions: std.DoublyLinkedList = .{}, node: std.DoublyLinkedList.Node = .{}, }; fn junctionPairCompareLT(junctions: []Junction, left: JunctionPair, right: JunctionPair) bool { return left.distanceSquared(junctions) < right.distanceSquared(junctions); } const Error = error { JunctionIdNotFound, }; fn findCircuitForJunction(circuits: std.DoublyLinkedList, junctionId: usize) !*std.DoublyLinkedList.Node { var circuitIter = circuits.first; while (circuitIter) |circuitNode| : (circuitIter = circuitNode.next) { const circuit: *Circuit = @fieldParentPtr("node", circuitNode); var found = false; var junctionIdIter = circuit.junctions.first; while (junctionIdIter) |node| : (junctionIdIter = node.next) { const junctionIdNode: *JunctionIdNode = @fieldParentPtr("node", node); if (junctionIdNode.id == junctionId) { found = true; break; } } if (found) { return circuitNode; } } return Error.JunctionIdNotFound; } pub fn main() !void { var fb_alloc = std.heap.FixedBufferAllocator.init(&allocatorBuffer); var allocator = fb_alloc.allocator(); const inputFile = try std.fs.cwd().openFile( "input.txt", .{ .mode = .read_only, }, ); defer inputFile.close(); var inputFileBuffer: [1024]u8 = undefined; var inputFileReader = inputFile.reader(&inputFileBuffer); const inputFileSize = try inputFileReader.getSize(); const inputBuffer = try allocator.alloc(u8, inputFileSize); try inputFileReader.interface.readSliceAll(inputBuffer); var junctions = std.ArrayList(Junction).empty; var i = std.mem.tokenizeScalar(u8, inputBuffer, '\n'); while (i.next()) |newJunctionText| { var j = std.mem.tokenizeAny(u8, newJunctionText, ",\n"); var newJunction = try junctions.addOne(allocator); newJunction.x = try std.fmt.parseInt(i64, j.next().?, 10); newJunction.y = try std.fmt.parseInt(i64, j.next().?, 10); newJunction.z = try std.fmt.parseInt(i64, j.next().?, 10); } var junctionPairs = std.ArrayList(JunctionPair).empty; for (0..junctions.items.len) |a| { for (a+1..junctions.items.len) |b| { var newJunctionPair = try junctionPairs.addOne(allocator); newJunctionPair.a = a; newJunctionPair.b = b; } } std.sort.block(JunctionPair, junctionPairs.items, junctions.items, junctionPairCompareLT); var junctionIdNodeStorage = try std.ArrayList(JunctionIdNode).initCapacity(allocator, junctions.items.len); var circuitsStorage = try std.ArrayList(Circuit).initCapacity(allocator, junctions.items.len); var circuits: std.DoublyLinkedList = .{}; for (0..junctions.items.len) |a| { var newJunctionIdNode = try junctionIdNodeStorage.addOne(allocator); newJunctionIdNode.id = a; var newCircuit = try circuitsStorage.addOne(allocator); newCircuit.junctions = .{}; newCircuit.junctions.append(&newJunctionIdNode.node); circuits.append(&newCircuit.node); } var circuitsCount:usize = junctions.items.len; for (0..junctionPairs.items.len) |wire| { const a = junctionPairs.items[wire].a; const b = junctionPairs.items[wire].b; const circuitANode = try findCircuitForJunction(circuits, a); const circuitBNode = try findCircuitForJunction(circuits, b); if (circuitANode == circuitBNode) { continue; } const circuitA: *Circuit = @fieldParentPtr("node", circuitANode); const circuitB: *Circuit = @fieldParentPtr("node", circuitBNode); circuitA.junctions.concatByMoving(&circuitB.junctions); circuits.remove(circuitBNode); circuitsCount -= 1; if (circuitsCount == 1) { try std.fs.File.stdout().writeAll( try std.fmt.bufPrint(&printBuffer, "{}\n", .{junctions.items[a].x*junctions.items[b].x})); break; } } }