From d5bd0322c7cad0e2a33d3d912dfaaee702706064 Mon Sep 17 00:00:00 2001
From: Lucia Ceionia <lucia@ceionia.com>
Date: Mon, 9 Dec 2024 01:08:30 -0600
Subject: [PATCH] day 9

---
 09/build.zig     |  67 ++++++++++++++++++++
 09/build.zig.zon |  72 +++++++++++++++++++++
 09/src/main.zig  | 159 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 298 insertions(+)
 create mode 100644 09/build.zig
 create mode 100644 09/build.zig.zon
 create mode 100644 09/src/main.zig

diff --git a/09/build.zig b/09/build.zig
new file mode 100644
index 0000000..4b50cf5
--- /dev/null
+++ b/09/build.zig
@@ -0,0 +1,67 @@
+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 = "09",
+        .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);
+    run_exe_unit_tests.has_side_effects = true;
+
+    // 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);
+}
diff --git a/09/build.zig.zon b/09/build.zig.zon
new file mode 100644
index 0000000..0d55eed
--- /dev/null
+++ b/09/build.zig.zon
@@ -0,0 +1,72 @@
+.{
+    // 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 = "09",
+
+    // 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",
+    },
+}
diff --git a/09/src/main.zig b/09/src/main.zig
new file mode 100644
index 0000000..5f60e74
--- /dev/null
+++ b/09/src/main.zig
@@ -0,0 +1,159 @@
+// okay zig is fine. ig.
+// i'm just bad at code, almost all the problems this time were
+// logic errors, not just me trying to figure the language out
+
+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 1" {
+    std.debug.print("\n", .{});
+    const value = try run1(test_data);
+    std.debug.print("{d}\n", .{value});
+    try std.testing.expectEqual(1928, value);
+}
+
+test "test input part 2" {
+    std.debug.print("\n",.{});
+    const value = try run2(test_data);
+    std.debug.print("{d}\n", .{value});
+    try std.testing.expectEqual(2858, value);
+}
+
+fn parseIntFromReader(reader: anytype) anyerror!u64 {
+    const f = try reader.readByte();
+    if (f < '0' or f > '9') return error.BadCharacter;
+    var v: u64 = f - '0';
+    while (true) {
+        const c = try reader.readByte();
+        if (c < '0' or c > '9') {
+            break;
+        } else {
+            v = (v * 10) + (c - '0');
+        }
+    }
+    return v;
+}
+
+// messy
+fn run2(input: []const u8) !u64 {
+    var copy = std.ArrayList(u8).init(alloc);
+    try copy.appendSlice(input);
+    var s = copy.items;
+    var last_nonzero = s.len-1;
+    if (last_nonzero&1==1) last_nonzero -= 1;
+    var start: usize = 0;
+    var position: usize = 0;
+    var total: u64 = 0;
+    var used_l = std.ArrayList(u8).init(alloc);
+    try used_l.appendNTimes('0', s.len);
+    var used = used_l.items;
+    while (start < s.len) {
+        // s[start] is used blocks
+        used: {
+            if (s[start] == '0') {
+                const endpos = position + used[start] - '0';
+                while (position < endpos) : (position += 1) {
+                }
+                break :used;
+            }
+            const endpos = position + s[start] - '0';
+            const id = start/2;
+            while (position < endpos) : (position += 1) {
+                total += position * id;
+            }
+        }
+
+        // s[start] is free blocks
+        start += 1;
+        free: { if (start < last_nonzero) {
+            const endpos = position + s[start] - '0';
+            while (position < endpos) {
+                const rem_size = endpos - position + '0';
+                // s[last_nonzero] is last used blocks
+                var t = last_nonzero;
+                while (s[t] == '0') { t -= 2; last_nonzero -= 2; }
+                while (s[t] == '0' or (s[t] > rem_size and t > start)) { t -= 2; }
+                if (t <= start) { 
+                    for ('0'..rem_size) |_| {
+                    }
+                    position = endpos;
+                    break :free;
+                }
+                const id = t/2;
+                const this_endpos = position + s[t] - '0';
+                while (position < this_endpos) : (position += 1) {
+                    total += position * id;
+                }
+                used[t] = s[t];
+                s[t] = '0';
+            }
+        } }
+
+        // next used block
+        start += 1;
+    }
+
+    return total;
+}
+
+fn run1(input: []const u8) !u64 {
+    var copy = std.ArrayList(u8).init(alloc);
+    try copy.appendSlice(input);
+    var s = copy.items;
+    var start: usize = 0;
+    var end: usize = s.len-1;
+    if (end&1==1) end -= 1;
+    var position: usize = 0;
+    var total: u64 = 0;
+    calc: while (start < end) {
+        // s[start] is used blocks
+        {
+            const endpos = position + s[start] - '0';
+            const id = start/2;
+            while (position < endpos) : (position += 1) {
+                total += position * id;
+            }
+        }
+
+        // s[start] is free blocks
+        start += 1;
+        {
+            const endpos = position + s[start] - '0';
+            // s[end] is last used blocks
+            var id = end/2;
+            while (position < endpos) : (position += 1) {
+                while (s[end] == '0') { end -= 2; id -= 1; if (end < start) break :calc; }
+                total += position * id;
+                s[end] -= 1;
+            }
+        }
+
+        // next used block
+        start += 1;
+    }
+    // any remaining i'm lazy
+    {
+        const endpos = position + s[start] - '0';
+        const id = start/2;
+        while (position < endpos) : (position += 1) {
+            total += position * id;
+        }
+    }
+
+    return total;
+}