133 lines
4.4 KiB
Zig
133 lines
4.4 KiB
Zig
const std = @import("std");
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pub const title = "Day 07: Laboratories";
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pub fn run(allocator: std.mem.Allocator) !void {
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const input = @embedFile("./input/day07.txt");
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//const input =
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// \\.......S.......
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// \\...............
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// \\.......^.......
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// \\...............
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// \\......^.^......
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// \\...............
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// \\.....^.^.^.....
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// \\...............
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// \\....^.^...^....
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// \\...............
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// \\...^.^...^.^...
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// \\...............
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// \\..^...^.....^..
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// \\...............
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// \\.^.^.^.^.^...^.
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// \\...............
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// ;
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var lines = std.mem.tokenizeScalar(u8, input, '\n');
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const first_line = lines.next() orelse unreachable;
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const starting_position = for (first_line, 0..) |c, i| {
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if (c == 'S') break i;
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} else unreachable;
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const line_len = first_line.len;
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std.debug.print("starting_position = {d}\n", .{starting_position});
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std.debug.print("{s}\n", .{first_line});
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const previous_line = try allocator.alloc(Cell, line_len);
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defer allocator.free(previous_line);
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var i: usize = 0;
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while (lines.next()) |line| {
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defer i += 1;
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const current_line = try allocator.alloc(Cell, line_len);
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defer allocator.free(current_line);
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for (line, 0..) |c, ci| {
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switch (c) {
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'.' => current_line[ci] = .empty,
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'^' => current_line[ci] = .splitter,
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else => unreachable, // There shouldn't be beams on this line yet!
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}
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}
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defer @memcpy(previous_line, current_line);
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defer {
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for (current_line) |cell| {
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std.debug.print("{f}", .{cell});
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}
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std.debug.print("\n", .{});
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}
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if (i == 0) {
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std.debug.assert(current_line[starting_position] == .empty);
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current_line[starting_position] = .{ .beam = .{ .timelines = 1 } };
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continue;
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}
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for (current_line, 0..) |cell, celli| {
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const previous_cell = previous_line[celli];
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if (previous_cell == .beam) {
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if (cell == .empty) {
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current_line[celli] = .{ .beam = .{ .timelines = previous_cell.beam.timelines } };
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} else if (cell == .splitter) {
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if (celli != 0) {
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const left = current_line[celli - 1];
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if (left == .empty) {
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current_line[celli - 1] = .{ .beam = .{ .timelines = previous_cell.beam.timelines } };
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} else if (left == .beam) {
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current_line[celli - 1] = .{ .beam = .{ .timelines = left.beam.timelines + previous_cell.beam.timelines } };
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}
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}
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if (celli != line_len - 1) {
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const right = current_line[celli + 1];
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if (right == .empty) {
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current_line[celli + 1] = .{ .beam = .{ .timelines = previous_cell.beam.timelines } };
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} else if (right == .beam) {
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current_line[celli + 1] = .{ .beam = .{ .timelines = right.beam.timelines + previous_cell.beam.timelines } };
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}
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}
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} else if (cell == .beam and previous_cell == .beam) {
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current_line[celli] = .{ .beam = .{ .timelines = cell.beam.timelines + previous_cell.beam.timelines } };
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}
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}
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}
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}
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var accumulator: usize = 0;
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for (previous_line) |cell| {
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accumulator += switch (cell) {
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.empty, .splitter => 0,
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.beam => |beam| beam.timelines,
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};
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}
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var buffer: [8]u8 = undefined;
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var stdout_writer = std.fs.File.stdout().writer(&buffer);
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const stdout = &stdout_writer.interface;
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try stdout.print("{d}\n", .{accumulator});
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try stdout.flush();
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}
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const Cell = union(enum) {
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empty: void,
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splitter: void,
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beam: struct {
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timelines: usize,
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},
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const Self = @This();
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pub fn format(self: Cell, w: *std.io.Writer) std.io.Writer.Error!void {
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switch (self) {
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.empty => try w.print(".", .{}),
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.splitter => try w.print("^", .{}),
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.beam => |beam| try w.print("{d}", .{beam.timelines}),
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}
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}
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};
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