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[2024] Added Day 09: Disk Fragmenter
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‎2024/09/disk_fragmenter/benchmarks/puzzle_benchmarks.zig‎

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const std = @import("std");
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const zbench = @import("zbench");
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const disk_fragmenter = @import("disk_fragmenter");
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const puzzle_input = @embedFile("puzzle_input");
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// Benchmark of part 1
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fn task_1(_: std.mem.Allocator) void {
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_ = disk_fragmenter.checksum_of_fragmented_disk(puzzle_input) catch {};
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}
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// Benchmark of part 2
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fn task_2(_: std.mem.Allocator) void {
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_ = disk_fragmenter.checksum_of_defragmented_disk(puzzle_input) catch {};
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}
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pub fn main() !void {
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const stdout = std.io.getStdOut().writer();
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var bench = zbench.Benchmark.init(std.heap.page_allocator, .{});
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defer bench.deinit();
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try bench.add("Day 09 - Task 1", task_1, .{});
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try bench.add("Day 09 - Task 2", task_2, .{});
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try stdout.writeAll("\n");
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try bench.run(stdout);
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}

‎2024/09/disk_fragmenter/build.zig‎

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const std = @import("std");
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pub fn build(b: *std.Build) void {
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const target = b.standardTargetOptions(.{});
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const optimize = b.standardOptimizeOption(.{});
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// -------------------------- Solution module --------------------------- \\
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const disk_fragmenter = b.addModule("disk_fragmenter", .{
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.root_source_file = b.path("src/disk_fragmenter.zig"),
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});
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// -------------------------- Main executable --------------------------- \\
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const disk_fragmenter_exe = b.addExecutable(.{
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.name = "disk_fragmenter",
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.root_source_file = b.path("src/main.zig"),
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.target = target,
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.optimize = optimize,
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});
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const yazap = b.dependency("yazap", .{});
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disk_fragmenter_exe.root_module.addImport("yazap", yazap.module("yazap"));
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disk_fragmenter_exe.root_module.addImport("disk_fragmenter", disk_fragmenter);
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b.installArtifact(disk_fragmenter_exe);
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const run_cmd = b.addRunArtifact(disk_fragmenter_exe);
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run_cmd.step.dependOn(b.getInstallStep());
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if (b.args) |args| {
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run_cmd.addArgs(args);
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}
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const run_step = b.step("run", "Run the disk_fragmenter (day 09) app");
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run_step.dependOn(&run_cmd.step);
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// --------------------------- Example tests ---------------------------- \\
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const disk_fragmenter_tests = b.addTest(.{
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.name = "disk_fragmenter_tests",
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.root_source_file = b.path("tests/example_tests.zig"),
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.target = target,
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.optimize = optimize,
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});
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disk_fragmenter_tests.root_module.addImport("disk_fragmenter", disk_fragmenter);
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disk_fragmenter_tests.root_module.addAnonymousImport("example_input", .{
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.root_source_file = b.path("input/example_input.txt"),
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});
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b.installArtifact(disk_fragmenter_tests);
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const test_step = b.step("test", "Run disk_fragmenter (day 09) tests");
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test_step.dependOn(&b.addRunArtifact(disk_fragmenter_tests).step);
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// ------------------------- Puzzle benchmarks -------------------------- \\
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const disk_fragmenter_benchmarks = b.addExecutable(.{
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.name = "disk_fragmenter_benchmarks",
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.root_source_file = b.path("benchmarks/puzzle_benchmarks.zig"),
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.target = target,
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.optimize = optimize,
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});
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const zbench = b.dependency("zbench", .{
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.target = target,
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.optimize = optimize,
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});
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disk_fragmenter_benchmarks.root_module.addImport("zbench", zbench.module("zbench"));
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disk_fragmenter_benchmarks.root_module.addImport("disk_fragmenter", disk_fragmenter);
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disk_fragmenter_benchmarks.root_module.addAnonymousImport("puzzle_input", .{
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.root_source_file = b.path("input/puzzle_input.txt"),
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});
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b.installArtifact(disk_fragmenter_benchmarks);
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const benchmark_step = b.step("benchmark", "Run disk_fragmenter (day 09) benchmarks");
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benchmark_step.dependOn(&b.addRunArtifact(disk_fragmenter_benchmarks).step);
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}

‎2024/09/disk_fragmenter/build.zig.zon‎

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.{
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.name = "disk_fragmenter",
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.version = "0.1.0",
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.minimum_zig_version = "0.13.0",
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.dependencies = .{
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.yazap = .{
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.url = "git+https://github.com/prajwalch/yazap#c2e3122d5dd6192513ba590f229dbc535110efb8",
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.hash = "122054439ec36ac10987c87ae69f3b041b40b2e451af3fe3ef1fc578b3bad756a800",
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},
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.zbench = .{
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.url = "git+https://github.com/hendriknielaender/zBench#fb3ecae5d035091fd2392a2ec21970c06fc375fa",
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.hash = "122095b73930ff5d627429295c669905d85bb9b54394ddc185ad2d61295cc65819e5",
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},
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},
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.paths = .{
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"build.zig",
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"build.zig.zon",
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"src",
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"input",
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"tests",
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"benchmarks",
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},
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}

‎2024/09/disk_fragmenter/input/example_input.txt‎

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2333133121414131402

‎2024/09/disk_fragmenter/input/puzzle_input.txt‎

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‎2024/09/disk_fragmenter/src/disk_fragmenter.zig‎

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const std = @import("std");
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const Allocator = std.mem.Allocator;
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const ArrayList = std.ArrayList;
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const string = []const u8;
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/// Task 1 - Compress the files on the disk while actively fragmenting the
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/// files. Return the checksum of the compressed disk.
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///
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/// Arguments:
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/// - `contents`: Input file contents.
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///
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/// Returns:
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/// - Checksum of the compressed (fragmented) disk.
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pub fn checksum_of_fragmented_disk(contents: string) !usize {
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var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
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defer arena.deinit();
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const allocator = arena.allocator();
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var files, var gaps = try parse_initial_disk(contents, allocator);
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var checksum: usize = 0;
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var files_front_idx: usize = 0;
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var files_back_idx: usize = files.items.len - 1;
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var disk_idx: usize = 0;
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var eof_idx: usize = 0;
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while (files_front_idx <= files_back_idx) {
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// Insert file
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eof_idx = disk_idx + files.items[files_front_idx] - 1;
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checksum += files_front_idx * partial_gauss_sum(disk_idx, eof_idx);
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disk_idx = eof_idx + 1;
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// Fill gap
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while (gaps.items[files_front_idx] > 0 and files_front_idx < files_back_idx) {
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if (files.items[files_back_idx] <= gaps.items[files_front_idx]) {
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eof_idx = disk_idx + files.items[files_back_idx] - 1;
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checksum += files_back_idx * partial_gauss_sum(disk_idx, eof_idx);
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disk_idx = eof_idx + 1;
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gaps.items[files_front_idx] -= files.items[files_back_idx];
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files_back_idx -= 1;
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} else {
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eof_idx = disk_idx + gaps.items[files_front_idx] - 1;
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checksum += files_back_idx * partial_gauss_sum(disk_idx, eof_idx);
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disk_idx = eof_idx + 1;
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files.items[files_back_idx] -= gaps.items[files_front_idx];
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gaps.items[files_front_idx] = 0;
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}
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}
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files_front_idx += 1;
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}
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return checksum;
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}
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/// Task 2 - Compress the files on the disk while preventing fragmentation of
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/// the files. Return the checksum of the compressed disk.
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///
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/// Arguments:
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/// - `contents`: Input file contents.
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///
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/// Returns:
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/// - Checksum of the compressed (defragmented) disk.
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pub fn checksum_of_defragmented_disk(contents: string) !usize {
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var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
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defer arena.deinit();
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const allocator = arena.allocator();
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const files, const gaps = try parse_initial_disk(contents, allocator);
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// Calculate initial disk locations
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var file_disk_locations = ArrayList(usize).init(allocator);
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var gap_disk_locations = ArrayList(usize).init(allocator);
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var disk_idx: usize = 0;
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for (0..files.items.len) |i| {
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try file_disk_locations.append(disk_idx);
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disk_idx += files.items[i];
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if (i < gaps.items.len) {
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try gap_disk_locations.append(disk_idx);
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disk_idx += gaps.items[i];
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}
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}
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// Move files where possible
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var file_idx = files.items.len;
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while (file_idx > 0) {
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file_idx -= 1;
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for (0..gaps.items.len) |gap_idx| {
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if (gap_disk_locations.items[gap_idx] > file_disk_locations.items[file_idx]) {
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break;
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}
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if (files.items[file_idx] <= gaps.items[gap_idx]) {
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file_disk_locations.items[file_idx] = gap_disk_locations.items[gap_idx];
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gap_disk_locations.items[gap_idx] += files.items[file_idx];
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gaps.items[gap_idx] -= files.items[file_idx];
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break;
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}
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}
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}
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// Calculate checksum
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var checksum: usize = 0;
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for (0..files.items.len) |i| {
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checksum += i * partial_gauss_sum(
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file_disk_locations.items[i],
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file_disk_locations.items[i] + files.items[i] - 1,
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);
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}
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return checksum;
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}
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// -------------------------------------------------------------------------- \\
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/// Sum all natural numbers between two given numbers.
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///
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/// Arguments:
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/// - `first`: The first number (lower bound).
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/// - `last`: The last number (upper bound).
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///
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/// Returns:
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/// - The sum of all natural numbers within the bounds.
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fn partial_gauss_sum(first: usize, last: usize) usize {
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return gauss_sum(last) - gauss_sum(first) + first;
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}
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/// Sum all natural numbers up to the given number.
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///
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/// Arguments:
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/// - `num`: The give number.
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///
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/// Returns:
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/// - The Gauss sum of the given number.
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fn gauss_sum(num: usize) usize {
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return num * (num + 1) / 2;
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}
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/// Parse the file contents into a list of file sizes and a list of gap sizes.
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///
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/// Arguments:
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/// - `contents`: Input file contents.
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/// - `allocator`: Allocator for the containers.
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///
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/// Returns:
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/// - Two lists with files sizes and gap sizes.
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fn parse_initial_disk(contents: string, allocator: Allocator) !struct { ArrayList(u32), ArrayList(u32) } {
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var files = ArrayList(u32).init(allocator);
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var gaps = ArrayList(u32).init(allocator);
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for (0..contents.len) |i| {
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if (i % 2 == 0) {
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try files.append(try std.fmt.parseInt(u32, contents[i..(i + 1)], 10));
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} else {
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try gaps.append(try std.fmt.parseInt(u32, contents[i..(i + 1)], 10));
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}
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}
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return .{ files, gaps };
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}

‎2024/09/disk_fragmenter/src/main.zig‎

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const std = @import("std");
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const yazap = @import("yazap");
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const disk_fragmenter = @import("disk_fragmenter");
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const allocator = std.heap.page_allocator;
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const log = std.log;
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const App = yazap.App;
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const Arg = yazap.Arg;
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const string = []const u8;
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pub fn main() !void {
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var app = App.init(allocator, "Day 09", "Day 09: Disk Fragmenter");
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defer app.deinit();
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var cmd = app.rootCommand();
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cmd.setProperty(.help_on_empty_args);
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try cmd.addArg(Arg.singleValueOption(
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"filename",
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'f',
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"Input file (e.g. input/puzzle_input.txt)",
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));
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const matches = try app.parseProcess();
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const stdout_file = std.io.getStdOut().writer();
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var bw = std.io.bufferedWriter(stdout_file);
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const stdout = bw.writer();
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var file_content: string = undefined;
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if (matches.getSingleValue("filename")) |filename| {
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const file = try std.fs.cwd().openFile(filename, .{});
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defer file.close();
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const file_size = try file.getEndPos();
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const buffer: []u8 = try allocator.alloc(u8, file_size);
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defer allocator.free(buffer);
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_ = try file.readAll(buffer);
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file_content = std.mem.Allocator.dupe(
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allocator,
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u8,
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std.mem.trim(u8, buffer, "\n"),
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) catch unreachable;
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} else {
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try app.displayHelp();
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return;
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}
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const result_1 = disk_fragmenter.checksum_of_fragmented_disk(file_content);
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try stdout.print("Checksum of fragmented compressed disk: {!}\n", .{result_1});
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try bw.flush();
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const result_2 = disk_fragmenter.checksum_of_defragmented_disk(file_content);
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try stdout.print("Checksum of defragmented compressed disk: {!}\n", .{result_2});
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try bw.flush();
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}

‎2024/09/disk_fragmenter/tests/example_tests.zig‎

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const std = @import("std");
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const disk_fragmenter = @import("disk_fragmenter");
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const testing = std.testing;
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// Test of part 1
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test "task_1" {
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const example_input = @embedFile("example_input");
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try testing.expectEqual(
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1928,
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disk_fragmenter.checksum_of_fragmented_disk(example_input),
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);
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}
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// Test of part 2
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test "task_2" {
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const example_input = @embedFile("example_input");
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try testing.expectEqual(
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2858,
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disk_fragmenter.checksum_of_defragmented_disk(example_input),
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);
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}

‎2024/build.zig‎

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add_subproject(b, target, optimize, test_step, benchmark_step, "02", "red_nosed_reports");
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add_subproject(b, target, optimize, test_step, benchmark_step, "03", "mull_it_over");
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add_subproject(b, target, optimize, test_step, benchmark_step, "06", "guard_gallivant");
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add_subproject(b, target, optimize, test_step, benchmark_step, "09", "disk_fragmenter");
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}

‎2024/build.zig.zon‎

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.day_02_red_nosed_reports = .{ .path = "02/red_nosed_reports" },
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.day_03_mull_it_over = .{ .path = "03/mull_it_over" },
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.day_06_guard_gallivant = .{ .path = "06/guard_gallivant" },
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.day_09_disk_fragmenter = .{ .path = "09/disk_fragmenter" },
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},
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.paths = .{
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"build.zig",
@@ -17,5 +18,6 @@
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"02",
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"03",
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"06",
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"09",
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},
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}

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