solve day 15

src/day14.zig

@@ -2,7 +2,6 @@ const std = @import("std");
 const aoc = @import("./aoc.zig");
 const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
-const PointU32 = @import("./point.zig").Point(u32);
 
 const Tile = enum {
     Empty,

src/day15.zig

@@ -0,0 +1,159 @@
+const std = @import("std");
+const aoc = @import("./aoc.zig");
+const assert = std.debug.assert;
+const Allocator = std.mem.Allocator;
+
+const Input = struct {
+    parts: std.ArrayList([]const u8),
+
+    fn init(allocator: Allocator) Input {
+        return Input{
+            .parts = std.ArrayList([]const u8).init(allocator)
+        };
+    }
+
+    fn deinit(self: Input) void {
+        self.parts.deinit();
+    }
+};
+
+const HashMapItem = struct {
+    key: []const u8,
+    value: u8
+};
+
+const HashMap = struct {
+    boxes: [256]std.ArrayList(HashMapItem),
+
+    fn init(allocator: Allocator) HashMap {
+        var boxes: [256]std.ArrayList(HashMapItem) = undefined;
+        for (0..256) |i| {
+            boxes[i] = std.ArrayList(HashMapItem).init(allocator);
+        }
+
+        return HashMap{ .boxes = boxes };
+    }
+
+    fn deinit(self: HashMap) void {
+        for (self.boxes) |box| {
+            box.deinit();
+        }
+    }
+
+    fn put(self: *HashMap, key: []const u8, value: u8) !void {
+        const hash = compute_hash(key);
+        var box = &self.boxes[hash];
+
+        for (box.items) |*item| {
+            if (std.mem.eql(u8, item.key, key)) {
+                item.value = value;
+                return;
+            }
+        }
+
+        try box.append(HashMapItem{ .key = key, .value = value });
+    }
+
+    fn remove(self: *HashMap, key: []const u8) void {
+        const hash = compute_hash(key);
+        var box = &self.boxes[hash];
+        for (0.., box.items) |i, item| {
+            if (std.mem.eql(u8, item.key, key)) {
+                _ = box.orderedRemove(i);
+                break;
+            }
+        }
+    }
+
+    fn debug(self: HashMap) void {
+        for (0.., self.boxes) |i, box| {
+            if (box.items.len == 0) continue;
+
+            std.debug.print("Box {}:", .{i});
+            for (box.items) |item| {
+                std.debug.print(" [{s} {}]", .{item.key, item.value});
+            }
+            std.debug.print("\n", .{});
+        }
+    }
+};
+
+fn parse_input(allocator: Allocator, lines: []const []const u8) !Input {
+    var result = Input.init(allocator);
+    errdefer result.deinit();
+
+    var iter = std.mem.splitScalar(u8, lines[0], ',');
+    while (iter.next()) |part| {
+        try result.parts.append(part);
+    }
+
+    return result;
+}
+
+fn compute_hash(text: []const u8) u8 {
+    var current: u16 = 0;
+    for (text) |symbol| {
+        current += symbol;
+        current *= 17;
+        current %= 256;
+    }
+    return @intCast(current);
+}
+
+pub fn part1(input: *aoc.Input) !aoc.Result {
+    const parsed = try parse_input(input.allocator, input.lines);
+    defer parsed.deinit();
+
+    var result: u64 = 0;
+    for (parsed.parts.items) |item| {
+        result += compute_hash(item);
+    }
+
+    return .{ .uint = result };
+}
+
+pub fn part2(input: *aoc.Input) !aoc.Result {
+    const allocator = input.allocator;
+    const parsed = try parse_input(input.allocator, input.lines);
+    defer parsed.deinit();
+
+    var hash_map = HashMap.init(allocator);
+    defer hash_map.deinit();
+
+    for (parsed.parts.items) |inst| {
+        if (inst[inst.len - 1] == '-') {
+            const key = inst[0..(inst.len-1)];
+            hash_map.remove(key);
+        } else {
+            const equal_pos = std.mem.indexOfScalar(u8, inst, '=') orelse return error.InvalidInstruction;
+            const key   = inst[0..equal_pos];
+            const value = inst[(equal_pos+1)] - '0';
+            try hash_map.put(key, value);
+        }
+
+        // std.debug.print("After \"{s}\":\n", .{inst});
+        // hash_map.debug();
+        // std.debug.print("\n", .{});
+    }
+
+    var result: u64 = 0;
+    for (1.., hash_map.boxes) |box_idx, box| {
+        for (1.., box.items) |item_idx, item| {
+            result += box_idx * item_idx * item.value;
+        }
+    }
+
+    return .{ .uint = result };
+}
+
+const example_input = [_][]const u8{
+    "rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7"
+};
+
+test "part 1 example" {
+    try aoc.expectAnswerUInt(part1, 1320, &example_input);
+}
+
+test "part 2 example" {
+    try aoc.expectAnswerUInt(part2, 145, &example_input);
+}

src/main.zig

@@ -35,6 +35,7 @@ const Days = [_]aoc.Day{
     create_day(@import("./day12.zig")),
     create_day(@import("./day13.zig")),
     create_day(@import("./day14.zig")),
+    create_day(@import("./day15.zig")),
 };
 
 fn kilobytes(count: u32) u32 {
@@ -73,10 +74,8 @@ fn run(allocator: Allocator, args: *cli) !u8 {
         lines.deinit();
     }
 
-    var line_buf: [1024]u8 = undefined;
-    while (try reader.readUntilDelimiterOrEof(&line_buf, '\n')) |line| {
-        var trimmed_line = std.mem.trimRight(u8, line, &.{'\r'});
-        try lines.append(try allocator.dupe(u8, trimmed_line));
+    while (try reader.readUntilDelimiterOrEofAlloc(allocator, '\n', kilobytes(32))) |line| {
+        try lines.append(std.mem.trimRight(u8, line, &.{'\r'}));
     }
 
     var input = aoc.Input{ .allocator = allocator, .lines = lines.items };
@@ -193,4 +192,5 @@ test {
     _ = @import("./day12.zig");
     _ = @import("./day13.zig");
     _ = @import("./day14.zig");
+    _ = @import("./day15.zig");
 }