day 7, part 2

day07-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 = "day07-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);
+}

day07-hard/sample.in

@@ -0,0 +1,5 @@
+32T3K 765
+T55J5 684
+KK677 28
+KTJJT 220
+QQQJA 483

day07-hard/src/main.zig

@@ -0,0 +1,219 @@
+const std = @import("std");
+
+fn StackList(comptime T: type, comptime capacity_type: type, comptime capacity: capacity_type) type {
+    return struct {
+        const Self = @This();
+        mem: [capacity]T,
+        length: capacity_type,
+
+        fn add(self: *Self, value: T) void {
+            self.mem[self.length] = value;
+            self.length += 1;
+        }
+
+        fn has(self: *Self, needle: T) bool {
+            for (0..self.length) |i| {
+                if (self.mem[i] == needle) {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        fn getMutableSlice(self: *Self) []T {
+            return (&self.mem)[0..self.length];
+        }
+
+        fn getSlice(self: *const Self) []const T {
+            return self.mem[0..self.length];
+        }
+
+        fn init() Self {
+            return Self{
+                .mem = undefined,
+                .length = 0,
+            };
+        }
+    };
+}
+
+const Rank = enum(u8) {
+    Five = 6,
+    Four = 5,
+    FullHouse = 4,
+    Three = 3,
+    TwoPair = 2,
+    OnePair = 1,
+    HighCard = 0,
+};
+
+const Hand = packed struct(u64) {
+    bid: u16,
+    card5: u8,
+    card4: u8,
+    card3: u8,
+    card2: u8,
+    card1: u8,
+    rank: Rank,
+};
+
+const HandSet = StackList(Hand, usize, 1000);
+
+fn parseCard(char: u8) u8 {
+    return switch (char) {
+        '2'...'9' => char - '0',
+        'T' => 10,
+        'J' => 1,
+        'Q' => 12,
+        'K' => 13,
+        'A' => 14,
+        else => unreachable,
+    };
+}
+
+fn getRank(cards: [5]u8) Rank {
+    var quantities = std.mem.zeroes([6]u8);
+    var jokers: u8 = 0;
+    for (cards) |first_card| {
+        if (first_card == 1) {
+            jokers += 1;
+            continue;
+        }
+
+        var matches: u4 = 0;
+        for (cards) |second_card| {
+            if (first_card == second_card) {
+                matches += 1;
+            }
+        }
+
+        quantities[matches] += 1;
+    }
+
+    if (jokers >= 4) {
+        return .Five;
+    }
+
+    if (jokers == 3) {
+        if (quantities[2] != 0) {
+            return .Five;
+        }
+
+        return .Four;
+    }
+
+    if (jokers == 2) {
+        if (quantities[3] != 0) {
+            return .Five;
+        }
+
+        if (quantities[2] != 0) {
+            return .Four;
+        }
+
+        return .Three;
+    }
+
+    if (jokers == 1) {
+        if (quantities[4] != 0) {
+            return .Five;
+        }
+
+        if (quantities[3] != 0) {
+            return .Four;
+        }
+
+        if (quantities[2] > 2) {
+            return .FullHouse;
+        }
+
+        if (quantities[2] > 0) {
+            return .Three;
+        }
+
+        return .OnePair;
+    }
+
+    if (quantities[5] != 0) {
+        return .Five;
+    }
+
+    if (quantities[4] != 0) {
+        return .Four;
+    }
+
+    if (quantities[3] != 0) {
+        if (quantities[2] != 0) {
+            return .FullHouse;
+        } else {
+            return .Three;
+        }
+    }
+
+    if (quantities[2] > 2) {
+        return .TwoPair;
+    }
+
+    if (quantities[2] != 0) {
+        return .OnePair;
+    }
+
+    return .HighCard;
+}
+
+fn addDigit(result: anytype, digit: u8) void {
+    result.* = (result.* * 10) + (digit - '0');
+}
+
+fn parseHand(line: []u8) Hand {
+    var cards: [5]u8 = undefined;
+    var i: usize = 0;
+    while (i < 5) : (i += 1) {
+        cards[i] = parseCard(line[i]);
+    }
+
+    var bid: u16 = 0;
+    i = 6;
+    while (i < line.len) : (i += 1) {
+        addDigit(&bid, line[i]);
+    }
+
+    return .{
+        .rank = getRank(cards),
+        .card1 = cards[0],
+        .card2 = cards[1],
+        .card3 = cards[2],
+        .card4 = cards[3],
+        .card5 = cards[4],
+        .bid = bid,
+    };
+}
+
+fn cmpByValue(context: void, a: Hand, b: Hand) bool {
+    return std.sort.asc(u64)(context, @bitCast(a), @bitCast(b));
+}
+
+fn solve(hands: *HandSet) u64 {
+    std.sort.heap(Hand, hands.getMutableSlice(), {}, cmpByValue);
+    var result: u64 = 0;
+    for (hands.getSlice(), 1..) |hand, i| {
+        result += i * hand.bid;
+    }
+    return result;
+}
+
+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 hands = HandSet.init();
+    var line_buffer: [1000]u8 = undefined;
+    while (try reader.readUntilDelimiterOrEof(&line_buffer, '\n')) |line| {
+        hands.add(parseHand(line));
+    }
+    try stdout.print("{d}\n", .{solve(&hands)});
+}