day 1

.gitignore

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+*/.zig-cache
+*/zig-out
+*/src/test
+*/src/input

01/build.zig

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+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+    // Standard target options allows the person running `zig build` to choose
+    // what target to build for. Here we do not override the defaults, which
+    // means any target is allowed, and the default is native. Other options
+    // for restricting supported target set are available.
+    const target = b.standardTargetOptions(.{});
+
+    // Standard optimization options allow the person running `zig build` to select
+    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
+    // set a preferred release mode, allowing the user to decide how to optimize.
+    const optimize = b.standardOptimizeOption(.{});
+
+    const exe = b.addExecutable(.{
+        .name = "01",
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // This declares intent for the executable to be installed into the
+    // standard location when the user invokes the "install" step (the default
+    // step when running `zig build`).
+    b.installArtifact(exe);
+
+    // This *creates* a Run step in the build graph, to be executed when another
+    // step is evaluated that depends on it. The next line below will establish
+    // such a dependency.
+    const run_cmd = b.addRunArtifact(exe);
+
+    // By making the run step depend on the install step, it will be run from the
+    // installation directory rather than directly from within the cache directory.
+    // This is not necessary, however, if the application depends on other installed
+    // files, this ensures they will be present and in the expected location.
+    run_cmd.step.dependOn(b.getInstallStep());
+
+    // This allows the user to pass arguments to the application in the build
+    // command itself, like this: `zig build run -- arg1 arg2 etc`
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+    }
+
+    // This creates a build step. It will be visible in the `zig build --help` menu,
+    // and can be selected like this: `zig build run`
+    // This will evaluate the `run` step rather than the default, which is "install".
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+
+    const exe_unit_tests = b.addTest(.{
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);
+
+    // Similar to creating the run step earlier, this exposes a `test` step to
+    // the `zig build --help` menu, providing a way for the user to request
+    // running the unit tests.
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_exe_unit_tests.step);
+}

01/build.zig.zon

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+.{
+    // This is the default name used by packages depending on this one. For
+    // example, when a user runs `zig fetch --save <url>`, this field is used
+    // as the key in the `dependencies` table. Although the user can choose a
+    // different name, most users will stick with this provided value.
+    //
+    // It is redundant to include "zig" in this name because it is already
+    // within the Zig package namespace.
+    .name = "01",
+
+    // This is a [Semantic Version](https://semver.org/).
+    // In a future version of Zig it will be used for package deduplication.
+    .version = "0.0.0",
+
+    // This field is optional.
+    // This is currently advisory only; Zig does not yet do anything
+    // with this value.
+    //.minimum_zig_version = "0.11.0",
+
+    // This field is optional.
+    // Each dependency must either provide a `url` and `hash`, or a `path`.
+    // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
+    // Once all dependencies are fetched, `zig build` no longer requires
+    // internet connectivity.
+    .dependencies = .{
+        // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+        //.example = .{
+        //    // When updating this field to a new URL, be sure to delete the corresponding
+        //    // `hash`, otherwise you are communicating that you expect to find the old hash at
+        //    // the new URL.
+        //    .url = "https://example.com/foo.tar.gz",
+        //
+        //    // This is computed from the file contents of the directory of files that is
+        //    // obtained after fetching `url` and applying the inclusion rules given by
+        //    // `paths`.
+        //    //
+        //    // This field is the source of truth; packages do not come from a `url`; they
+        //    // come from a `hash`. `url` is just one of many possible mirrors for how to
+        //    // obtain a package matching this `hash`.
+        //    //
+        //    // Uses the [multihash](https://multiformats.io/multihash/) format.
+        //    .hash = "...",
+        //
+        //    // When this is provided, the package is found in a directory relative to the
+        //    // build root. In this case the package's hash is irrelevant and therefore not
+        //    // computed. This field and `url` are mutually exclusive.
+        //    .path = "foo",
+
+        //    // When this is set to `true`, a package is declared to be lazily
+        //    // fetched. This makes the dependency only get fetched if it is
+        //    // actually used.
+        //    .lazy = false,
+        //},
+    },
+
+    // Specifies the set of files and directories that are included in this package.
+    // Only files and directories listed here are included in the `hash` that
+    // is computed for this package. Only files listed here will remain on disk
+    // when using the zig package manager. As a rule of thumb, one should list
+    // files required for compilation plus any license(s).
+    // Paths are relative to the build root. Use the empty string (`""`) to refer to
+    // the build root itself.
+    // A directory listed here means that all files within, recursively, are included.
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        //"README.md",
+    },
+}

01/src/main.zig

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+// Okay! First time using zig!
+// The compiler warnings are worse than C's.
+// But whatever, I'm starting to get used to some of it?
+// I think?
+// Still nowhere near idiomatic, sure I'm missing lots of better ways
+// But hey! It worked
+
+const std = @import("std");
+
+var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+const alloc = arena.allocator();
+
+const test_data = @embedFile("test");
+const input_data = @embedFile("input");
+
+pub fn main() !void {
+    const stdout = std.io.getStdOut().writer();
+
+    const value1 = try run1(input_data);
+    try stdout.print("{d}\n", .{value1});
+
+    const value2 = try run2(input_data);
+    try stdout.print("{d}\n", .{value2});
+}
+
+test "test input part 2" {
+    const value = try run2(test_data);
+    std.debug.print("{d}\n", .{value});
+    try std.testing.expectEqual(value, 31);
+}
+
+test "test input part 1" {
+    const value = try run1(test_data);
+    std.debug.print("{d}\n", .{value});
+    try std.testing.expectEqual(value, 11);
+}
+
+fn run2(s: []const u8) !i64 {
+    var arrs = [_]std.ArrayList(i64){ std.ArrayList(i64).init(alloc), std.ArrayList(i64).init(alloc) };
+
+    var lines = std.mem.splitScalar(u8, s, '\n');
+    while (lines.next()) |line| {
+        std.debug.print("{s}\n", .{line});
+        var split = std.mem.splitScalar(u8, line, ' ');
+        var c: u8 = 0;
+        while (split.next()) |i| {
+            // idk how to put this inside the while
+            if (c >= 2) break;
+            if (std.mem.eql(u8, i, "")) continue;
+            const num = try std.fmt.parseInt(i64, i, 10);
+            try arrs[c].append(num);
+            c += 1;
+        }
+    }
+
+    // this is a lot of recalc, but these lists aren't that long so whatever
+    // i think it's O(n) so good enough
+    var sim_score: i64 = 0;
+    for (arrs[0].items) |x| {
+        for (arrs[1].items) |y| {
+            if (x == y) {
+                sim_score += x;
+            }
+        }
+    }
+
+    return sim_score;
+}
+
+fn run1(s: []const u8) !u64 {
+    var arrs = [_]std.ArrayList(i64){ std.ArrayList(i64).init(alloc), std.ArrayList(i64).init(alloc) };
+
+    var lines = std.mem.splitScalar(u8, s, '\n');
+    while (lines.next()) |line| {
+        std.debug.print("{s}\n", .{line});
+        var split = std.mem.splitScalar(u8, line, ' ');
+        var c: u8 = 0;
+        while (split.next()) |i| {
+            // idk how to put this inside the while
+            if (c >= 2) break;
+            if (std.mem.eql(u8, i, "")) continue;
+            const num = try std.fmt.parseInt(i64, i, 10);
+            try arrs[c].append(num);
+            c += 1;
+        }
+    }
+
+    for (arrs) |arr| {
+        std.mem.sort(i64, arr.items, {}, comptime std.sort.asc(i64));
+    }
+
+    for (arrs) |arr| {
+        for (arr.items) |e| {
+            std.debug.print("{d} ", .{e});
+        }
+        std.debug.print("\n", .{});
+    }
+
+    var total_dist: u64 = 0;
+    const len = arrs[0].items.len;
+    for (0..len) |i| {
+        total_dist += @abs(arrs[0].items[i] - arrs[1].items[i]);
+    }
+
+    return total_dist;
+}