day2, part 2

day02-hard/build.zig

@@ -0,0 +1,70 @@
+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 = "day02-hard",
+        // In this case the main source file is merely a path, however, in more
+        // complicated build scripts, this could be a generated file.
+        .root_source_file = .{ .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);
+
+    // Creates a step for unit testing. This only builds the test executable
+    // but does not run it.
+    const unit_tests = b.addTest(.{
+        .root_source_file = .{ .path = "src/main.zig" },
+        .target = target,
+        .optimize = optimize,
+    });
+
+    const run_unit_tests = b.addRunArtifact(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_unit_tests.step);
+}

day02-hard/sample.in

@@ -0,0 +1,5 @@
+Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green
+Game 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue
+Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red
+Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red
+Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green

day02-hard/src/main.zig

@@ -0,0 +1,97 @@
+const std = @import("std");
+
+const Cubes = struct {
+    red: u32 = 0,
+    green: u32 = 0,
+    blue: u32 = 0,
+
+    fn getPower(self: *Cubes) u32 {
+        return self.red * self.green * self.blue;
+    }
+
+    fn setRed(self: *Cubes, value: u32) void {
+        if (self.red < value) {
+            self.red = value;
+        }
+    }
+
+    fn setGreen(self: *Cubes, value: u32) void {
+        if (self.green < value) {
+            self.green = value;
+        }
+    }
+
+    fn setBlue(self: *Cubes, value: u32) void {
+        if (self.blue < value) {
+            self.blue = value;
+        }
+    }
+};
+
+fn solve(line: []const u8) u32 {
+    var current_number: u32 = 0;
+    var current_pick = Cubes{};
+
+    var index: usize = 0;
+    while (index < line.len) : (index += 1) {
+        const char = line[index];
+        switch (char) {
+            '0'...'9' => {
+                current_number = current_number * 10 + (char - '0');
+            },
+            'G' => {
+                index += 4;
+            },
+            ':' => {
+                current_number = 0;
+            },
+            ' ' => {},
+            ',' => {},
+            'r' => {
+                current_pick.setRed(current_number);
+                current_number = 0;
+                index += 2;
+            },
+            'g' => {
+                current_pick.setGreen(current_number);
+                current_number = 0;
+                index += 4;
+            },
+            'b' => {
+                current_pick.setBlue(current_number);
+                current_number = 0;
+                index += 3;
+            },
+            ';' => {},
+            else => unreachable,
+        }
+    }
+
+    return current_pick.getPower();
+}
+
+pub fn main() !void {
+    const stdout = std.io.getStdOut().writer();
+
+    const raw_in = std.io.getStdIn();
+    var buffered_reader = std.io.bufferedReader(raw_in.reader());
+    var reader = buffered_reader.reader();
+
+    var result: u32 = 0;
+    var line_buffer: [1000]u8 = undefined;
+    while (try reader.readUntilDelimiterOrEof(&line_buffer, '\n')) |line| {
+        result += solve(line);
+    }
+    try stdout.print(
+        "{d}\n",
+        .{result},
+    );
+}
+
+test "solve" {
+    try std.testing.expectEqual(@as(?u32, 48), solve("Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green"));
+    try std.testing.expectEqual(@as(?u32, 12), solve("Game 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue"));
+    try std.testing.expectEqual(@as(?u32, 1560), solve("Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red"));
+    try std.testing.expectEqual(@as(?u32, 630), solve("Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red"));
+    try std.testing.expectEqual(@as(?u32, 36), solve("Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green"));
+}