day07 part1

src/day07.zig

@@ -0,0 +1,136 @@
+const std = @import("std");
+const util = @import("util.zig");
+const mem = std.mem;
+
+pub fn main() !void {
+    const input = @embedFile("data/day07.txt");
+    const sln = try solve(util.gpa, input);
+    std.debug.print("{d}\n", .{sln.a});
+    std.debug.print("{d}\n", .{sln.b});
+}
+
+const Cards = [5]u8;
+
+const Solution = struct {
+    a: usize,
+    b: usize,
+};
+
+const Score = enum(u8) {
+    fiveKind,
+    fourKind,
+    fullHouse,
+    threeKind,
+    twoPair,
+    onePair,
+    high,
+};
+
+const Hand = struct {
+    cards: [5]u8,
+    bid: u32,
+    score: Score,
+};
+
+fn fixCards(cards: *[5]u8) void {
+    for (cards, 0..) |card, i| {
+        cards[i] = switch (card) {
+            'A' => 13,
+            'K' => 12,
+            'Q' => 11,
+            'J' => 10,
+            'T' => 9,
+            '2'...'9' => card - '2',
+            else => unreachable,
+        };
+    }
+}
+
+fn u8gt(context: void, a: u8, b: u8) bool {
+    _ = context;
+    return a > b;
+}
+
+fn scoreHand(cards: Cards) Score {
+    var dups: [14]u8 = undefined;
+    @memset(&dups, 0);
+    for (cards) |a| {
+        dups[a] += 1;
+    }
+    std.mem.sort(u8, &dups, {}, u8gt);
+    return switch (dups[0]) {
+        5 => .fiveKind,
+        4 => .fourKind,
+        3 => if (dups[1] == 2) .fullHouse else .threeKind,
+        2 => if (dups[1] == 2) .twoPair else .onePair,
+        else => .high,
+    };
+}
+
+fn compareHand(context: void, a: Hand, b: Hand) bool {
+    _ = context;
+    if (a.score != b.score) {
+        return @intFromEnum(a.score) > @intFromEnum(b.score);
+    } else {
+        for (a.cards, b.cards) |cardA, cardB| {
+            if (cardA != cardB) return cardA < cardB;
+        }
+    }
+    unreachable;
+}
+
+fn sortHands(hands: *std.ArrayList(Hand)) !void {
+    std.mem.sort(Hand, hands.items, {}, compareHand);
+}
+
+fn solve(alloc: mem.Allocator, input: []const u8) !Solution {
+    var hands = try std.ArrayList(Hand).initCapacity(alloc, 1001);
+    defer hands.deinit();
+
+    var it = util.splitLines(input);
+    while (it.next()) |line| {
+        if (line.len == 0) continue;
+
+        var cards = line[0..5].*;
+        fixCards(&cards);
+        const bid = try std.fmt.parseInt(u32, line[6..], 10);
+        const score = scoreHand(cards);
+        const hand = Hand{ .cards = cards, .bid = bid, .score = score };
+        try hands.append(hand);
+    }
+
+    // std.debug.print("{any}\n", .{hands.items});
+    try sortHands(&hands);
+
+    var partA: usize = 0;
+    for (hands.items, 1..) |hand, rank| {
+        // std.debug.print("{d} * {d}\n", .{ hand.bid, rank });
+        partA += hand.bid * rank;
+    }
+
+    return .{ .a = partA, .b = 0 };
+}
+
+test "silver" {
+    const input =
+        \\32T3K 765
+        \\T55J5 684
+        \\KK677 28
+        \\KTJJT 220
+        \\QQQJA 483
+    ;
+    const sln = try solve(std.testing.allocator, input);
+    try std.testing.expectEqual(@as(usize, 6440), sln.a);
+}
+
+test "gold" {
+    const input =
+        \\32T3K 765
+        \\T55J5 684
+        \\KK677 28
+        \\KTJJT 220
+        \\QQQJA 483
+    ;
+    const sln = try solve(std.testing.allocator, input);
+    try std.testing.expectEqual(@as(usize, 0), sln.b);
+}