Merge branch 'day12'

This feels like cheating

src/days/day12.zig

@@ -1,7 +1,240 @@
 const std = @import("std");
 
-pub const title = "Day 12";
+pub const title = "Day 12: Christmas Tree Farm";
 
-pub fn run(_: std.mem.Allocator) !void {
+pub fn run(allocator: std.mem.Allocator) !void {
+    const input = @embedFile("./input/day12.txt");
+    //const input =
+    //    \\0:
+    //    \\###
+    //    \\##.
+    //    \\##.
+    //    \\
+    //    \\1:
+    //    \\###
+    //    \\##.
+    //    \\.##
+    //    \\
+    //    \\2:
+    //    \\.##
+    //    \\###
+    //    \\##.
+    //    \\
+    //    \\3:
+    //    \\##.
+    //    \\###
+    //    \\##.
+    //    \\
+    //    \\4:
+    //    \\###
+    //    \\#..
+    //    \\###
+    //    \\
+    //    \\5:
+    //    \\###
+    //    \\.#.
+    //    \\###
+    //    \\
+    //    \\4x4: 0 0 0 0 2 0
+    //    \\12x5: 1 0 1 0 2 2
+    //    \\12x5: 1 0 1 0 3 2
+    //    ;
+
+    var lines = std.mem.tokenizeScalar(u8, input, '\n');
+
+    var presents: std.ArrayList(Present) = .empty;
+    defer presents.deinit(allocator);
+
+    var regions: std.ArrayList(Region) = .empty;
+    defer {
+        for (regions.items) |region| {
+            region.deinit(allocator);
+        }
+        regions.deinit(allocator);
+    }
+
+    while (lines.next()) |line| {
+        var semicolon_pos: usize = 0;
+        var x_pos: ?usize = null;
+        for (line, 0..) |c, i| {
+            switch (c) {
+                'x' => x_pos = i,
+                ':' => {
+                    semicolon_pos = i;
+                    break;
+                },
+                else => {},
+            }
+        }
+        if (semicolon_pos != 0) {
+            if (x_pos) |p| {
+                // region
+                const width = try std.fmt.parseUnsigned(usize, line[0..p], 10);
+                const height = try std.fmt.parseUnsigned(usize, line[p + 1..semicolon_pos], 10);
+
+                var required_presents: std.ArrayList(u8) = .empty;
+                defer required_presents.deinit(allocator);
+                if (presents.items.len > 0) {
+                    try required_presents.ensureTotalCapacity(allocator, presents.items.len);
+                }
+
+                var presents_iter = std.mem.tokenizeScalar(u8, line[semicolon_pos + 2..], ' ');
+                while (presents_iter.next()) |present| {
+                    const amount = try std.fmt.parseUnsigned(u8, present, 10);
+                    try required_presents.append(allocator, amount);
+                }
+
+                const required_presents_slice = try required_presents.toOwnedSlice(allocator);
+                errdefer allocator.free(required_presents_slice);
+
+                const region: Region = .{
+                    .width = width,
+                    .height = height,
+                    .required_presents = required_presents_slice,
+                };
+                try regions.append(allocator, region);
+            } else {
+                // present
+                var present: Present = .{
+                    .shape = .initEmpty(),
+                };
+                for (0..Present.Width) |y| {
+                    const l = lines.next() orelse unreachable;
+                    for (0..Present.Width) |x| {
+                        if (l[x] == '#') {
+                            present.set(x, y);
+                        }
+                    }
+                }
+                try presents.append(allocator, present);
+            }
+        }
+    }
+
+    var accumulator: usize = 0;
+
+    for (regions.items) |region| {
+        std.debug.print("{f}\n", .{region});
+        var area_needed: usize = 0;
+        for (region.required_presents, 0..) |amount, i| {
+            area_needed += amount * presents.items[i].area();
+        }
+        if (area_needed < region.area()) {
+            std.debug.print("{f}\nfits\n", .{region});
+            accumulator += 1;
+        }
+    }
+
+    var buffer: [8]u8 = undefined;
+    var stdout_writer = std.fs.File.stdout().writer(&buffer);
+    const stdout = &stdout_writer.interface;
+
+    try stdout.print("{d}\n", .{accumulator});
+
+    try stdout.flush();
 }
 
+const Present = struct {
+    shape: std.bit_set.IntegerBitSet(Width * Width),
+
+    const Width = 3;
+
+    const Self = @This();
+
+    pub fn format(self: Self, w: *std.Io.Writer) std.Io.Writer.Error!void {
+        for (0..Width) |y| {
+            for (0..Width) |x| {
+                try w.writeByte(if (self.isSet(x, y)) '#' else '.');
+            }
+            if (y < Width - 1) {
+                try w.writeByte('\n');
+            }
+        }
+    }
+
+    pub fn set(self: *Self, x: usize, y: usize) void {
+        const index = (y * Width) + x;
+        self.shape.set(index);
+    }
+
+    pub fn isSet(self: Self, x: usize, y: usize) bool {
+        const index = (y * Width) + x;
+        return self.shape.isSet(index);
+    }
+
+    pub fn area(self: Self) usize {
+        return self.shape.count();
+    }
+};
+
+const Region = struct {
+    width: usize,
+    height: usize,
+    required_presents: []u8,
+
+    const Self = @This();
+
+    pub fn deinit(self: Self, allocator: std.mem.Allocator) void {
+        allocator.free(self.required_presents);
+    }
+
+    pub fn format(self: Self, w: *std.Io.Writer) std.Io.Writer.Error!void {
+        try w.print("{d}x{d}: ", .{self.width, self.height});
+        for (self.required_presents, 0..) |present, i| {
+            try w.print("{d}", .{present});
+            if (i < self.required_presents.len - 1) {
+                try w.writeByte(' ');
+            }
+        }
+    }
+
+    pub fn createEmpty(self: Self, allocator: std.mem.Allocator) !EmptyRegion {
+        return try .init(allocator, self.width, self.height);
+    }
+
+    pub fn area(self: Self) usize {
+        return self.width * self.height;
+    }
+};
+
+const EmptyRegion = struct {
+    grid: [][]bool,
+    filled_spaces: usize,
+
+    allocator: std.mem.Allocator,
+
+    const Self = @This();
+
+    pub fn init(allocator: std.mem.Allocator, width: u8, height: u8) !Self {
+        const h = try allocator.alloc([]bool, height);
+        for (0..height) |i| {
+            const w = try allocator.alloc(u8, width);
+            @memset(w, false);
+            h[i] = w;
+        }
+        return .{
+            .grid = h,
+            .filled_spaces = 0,
+            .allocator = allocator,
+        };
+    }
+
+    pub fn deinit(self: Self) void {
+        for (self.grid) |row| {
+            self.allocator.free(row);
+        }
+        self.allocator.free(self.grid);
+    }
+
+    pub fn fits(self: Self, present: Present) bool {
+        std.debug.assert(self.grid.len > 0);
+        const size = self.grid.len * self.grid[0].len;
+        if ((size - self.filled_spaces) < present.shape.count()) {
+            return false;
+        }
+
+        // TODO: Implementation
+        return false;
+    }
+};
+