feat(day22)

AdventOfCode2023/.gitignore

@@ -1,3 +1,4 @@
+.zig-cache
 zig-cache
 zig-out
 input.txt

AdventOfCode2023/src/day22/day22.zig

@@ -0,0 +1,275 @@
+const std = @import("std");
+
+const print = std.debug.print;
+const expect = std.testing.expect;
+
+const Node = struct {
+    index: usize,
+    leaf: []Node,
+
+    pub fn pretty_print(self: Node, indent: usize) void {
+        for (0..indent) |_| {
+            print(" ", .{});
+        }
+
+        print("-> {}\n", .{self.index});
+        for (self.leaf) |leaf| {
+            leaf.pretty_print(indent + 1);
+        }
+    }
+};
+
+const Brick = struct {
+    min_x: usize,
+    min_y: usize,
+    min_z: usize,
+
+    max_x: usize,
+    max_y: usize,
+    max_z: usize,
+
+    supported_by: []usize,
+    supports: []usize,
+
+    pub fn create(x1: usize, y1: usize, z1: usize, x2: usize, y2: usize, z2: usize) Brick {
+        const min_x = if (x1 > x2) x2 else x1;
+        const min_y = if (y1 > y2) y2 else y1;
+        const min_z = if (z1 > z2) z2 else z1;
+
+        const max_x = if (x1 < x2) x2 else x1;
+        const max_y = if (y1 < y2) y2 else y1;
+        const max_z = if (z1 < z2) z2 else z1;
+
+        return Brick{ .supported_by = &[_]usize{}, .supports = &[_]usize{}, .min_x = min_x, .min_y = min_y, .min_z = min_z, .max_x = max_x, .max_y = max_y, .max_z = max_z };
+    }
+
+    pub fn deinit(self: Brick) void {
+        self.supports.deinit();
+        self.supported_by.deinit();
+    }
+
+    pub fn overlaps(self: Brick, other: Brick) bool {
+        if (self.min_x > other.max_x or other.min_x > self.max_x) {
+            return false;
+        }
+
+        if (self.min_y > other.max_y or other.min_y > self.max_y) {
+            return false;
+        }
+
+        return true;
+    }
+
+    pub fn is_above(self: Brick, other: Brick) bool {
+        return self.min_z > other.max_z;
+    }
+
+    /// Is self right above other.
+    pub fn is_right_above(self: Brick, other: Brick) bool {
+        return self.min_z == other.max_z + 1;
+    }
+};
+
+fn compareBricks(_: void, brick1: Brick, brick2: Brick) bool {
+    return brick1.min_z < brick2.min_z;
+}
+
+fn is_something_below(bricks: []Brick, brick: Brick, current_index: usize) bool {
+    if (brick.min_z == 1) {
+        // The floor is below us.
+        return true;
+    }
+
+    for (bricks, 0..) |other_brick, index| {
+        if (index == current_index) {
+            continue;
+        }
+
+        if (!brick.is_above(other_brick)) {
+            continue;
+        }
+
+        if (brick.overlaps(other_brick) and brick.is_right_above(other_brick)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+fn doesnt_causes_falling(bricks: []Brick, brick: Brick) bool {
+    return for (brick.supports) |brick_supporting_index| {
+        const supported_brick = bricks[brick_supporting_index];
+
+        if (supported_brick.supported_by.len == 1) {
+            break false;
+        }
+    } else true;
+}
+
+fn count(counted_bricks: *std.AutoHashMap(usize, bool), bricks: []Brick, brick_index: usize) usize {
+    var c: usize = 0;
+
+    counted_bricks.put(brick_index, true) catch unreachable;
+
+    for (bricks[brick_index].supports) |supported_brick_index| {
+        if (counted_bricks.get(supported_brick_index) != null) {
+            continue;
+        }
+
+        const all_in_map = for (bricks[supported_brick_index].supported_by) |supported_by_index| {
+            if (counted_bricks.get(supported_by_index) == null) {
+                break false;
+            }
+        } else true;
+
+        if (!all_in_map) {
+            continue;
+        }
+
+        counted_bricks.put(supported_brick_index, true) catch unreachable;
+
+        c += 1 + count(counted_bricks, bricks, supported_brick_index);
+    }
+
+    return c;
+}
+
+pub fn solve(input: [][]const u8) !void {
+    const allocator = std.heap.page_allocator;
+
+    var bricks = try allocator.alloc(Brick, input.len);
+    defer allocator.free(bricks);
+
+    for (0..bricks.len) |index| {
+        const tilda_index: usize = for (input[index], 0..) |c, c_index| {
+            if (c == '~') {
+                break c_index;
+            }
+        } else unreachable;
+
+        const first_coord = input[index][0..tilda_index];
+        const second_coord = input[index][tilda_index + 1 ..];
+
+        var first_comma_tokenizer = std.mem.tokenizeSequence(u8, first_coord, ",");
+
+        const x1 = try std.fmt.parseInt(usize, first_comma_tokenizer.next().?, 10);
+        const y1 = try std.fmt.parseInt(usize, first_comma_tokenizer.next().?, 10);
+        const z1 = try std.fmt.parseInt(usize, first_comma_tokenizer.next().?, 10);
+
+        var second_comma_tokenizer = std.mem.tokenizeSequence(u8, second_coord, ",");
+
+        const x2 = try std.fmt.parseInt(usize, second_comma_tokenizer.next().?, 10);
+        const y2 = try std.fmt.parseInt(usize, second_comma_tokenizer.next().?, 10);
+        const z2 = try std.fmt.parseInt(usize, second_comma_tokenizer.next().?, 10);
+
+        bricks[index] = Brick.create(x1, y1, z1, x2, y2, z2);
+    }
+
+    std.mem.sort(Brick, bricks, {}, comptime compareBricks);
+
+    var fallen_bricks = try allocator.alloc(Brick, bricks.len);
+
+    for (bricks, 0..) |brick, brick_index| {
+        var working_brick = brick;
+
+        while (!is_something_below(fallen_bricks, working_brick, brick_index)) {
+            working_brick.min_z -= 1;
+            working_brick.max_z -= 1;
+        }
+
+        fallen_bricks[brick_index] = working_brick;
+    }
+
+    for (0..fallen_bricks.len) |brick_index| {
+        for (brick_index + 1..fallen_bricks.len) |other_brick_index| {
+            var brick = fallen_bricks[brick_index];
+            var other_brick = fallen_bricks[other_brick_index];
+
+            if (!brick.overlaps(other_brick)) {
+                continue;
+            }
+
+            if (!other_brick.is_right_above(brick)) {
+                continue;
+            }
+
+            other_brick.supported_by = try allocator.realloc(other_brick.supported_by, other_brick.supported_by.len + 1);
+            brick.supports = try allocator.realloc(brick.supports, brick.supports.len + 1);
+
+            other_brick.supported_by[other_brick.supported_by.len - 1] = brick_index;
+            brick.supports[brick.supports.len - 1] = other_brick_index;
+
+            fallen_bricks[brick_index] = brick;
+            fallen_bricks[other_brick_index] = other_brick;
+        }
+    }
+
+    var part1: usize = 0;
+
+    for (fallen_bricks) |brick| {
+        if (brick.supports.len == 0) {
+            part1 += 1;
+            continue;
+        }
+
+        if (doesnt_causes_falling(fallen_bricks, brick)) {
+            part1 += 1;
+        }
+    }
+
+    var part2: usize = 0;
+
+    for (fallen_bricks, 0..) |brick, index| {
+        if (doesnt_causes_falling(fallen_bricks, brick)) {
+            continue;
+        }
+
+        var used_bricks = std.AutoHashMap(usize, bool).init(allocator);
+        defer used_bricks.deinit();
+
+        part2 += count(&used_bricks, fallen_bricks, index);
+    }
+
+    print("Part 1: {}\n", .{part1});
+    print("Part 2: {}\n", .{part2});
+}
+
+test "Bricks overlap" {
+    const brick1 = Brick{ .supported_by = undefined, .supports = undefined, .min_x = 0, .min_y = 0, .min_z = 0, .max_x = 3, .max_y = 3, .max_z = 3 };
+    const brick2 = Brick{ .supported_by = undefined, .supports = undefined, .min_x = 1, .min_y = 1, .min_z = 1, .max_x = 2, .max_y = 2, .max_z = 2 };
+
+    try expect(brick1.overlaps(brick2));
+}
+
+test "Bricks dont overlap" {
+    const brick1 = Brick{ .supported_by = undefined, .supports = undefined, .min_x = 0, .min_y = 0, .min_z = 0, .max_x = 3, .max_y = 3, .max_z = 3 };
+    const brick2 = Brick{ .supported_by = undefined, .supports = undefined, .min_x = 1, .min_y = 10, .min_z = 1, .max_x = 2, .max_y = 20, .max_z = 2 };
+
+    try expect(!brick1.overlaps(brick2));
+
+    const brick3 = Brick{
+        .supported_by = undefined,
+        .supports = undefined,
+        .min_x = 0,
+        .min_y = 0,
+        .min_z = 2,
+        .max_x = 2,
+        .max_y = 0,
+        .max_z = 2,
+    };
+
+    const brick4 = Brick{
+        .supported_by = undefined,
+        .supports = undefined,
+        .min_x = 0,
+        .min_y = 2,
+        .min_z = 3,
+        .max_x = 2,
+        .max_y = 2,
+        .max_z = 3,
+    };
+
+    try expect(!brick3.overlaps(brick4));
+    try expect(!brick4.overlaps(brick3));
+}

AdventOfCode2023/src/main.zig

@@ -17,16 +17,17 @@ const std = @import("std");
 // const day17 = @import("./day17/day17.zig");
 // const day18 = @import("./day18/day18.zig");
 // const day19 = @import("./day19/day19.zig");
-const day20 = @import("./day20/day20.zig");
+// const day20 = @import("./day20/day20.zig");
 // const day21 = @import("./day21/day21.zig");
+const day22 = @import("./day22/day22.zig");
 // const day23 = @import("./day23/day23.zig");
 // const day24 = @import("./day24/day24.zig");
 const utils = @import("utils.zig");
 
 pub fn main() !void {
     const allocator = std.heap.page_allocator;
-    const input = try utils.getInput("./src/day20/input.txt", allocator);
+    const input = try utils.getInput("./src/day22/input.txt", allocator);
     defer allocator.free(input);
 
-    try day20.solve(input);
+    try day22.solve(input);
 }

AdventOfCode2023/src/utils.zig

@@ -9,7 +9,7 @@ pub fn getInput(fileName: []const u8, allocator: mem.Allocator) !([][]u8) {
     var lines = ArrayList([]u8).init(allocator);
     defer lines.deinit();
 
-    var iterator = mem.split(u8, content, "\n");
+    var iterator = mem.splitSequence(u8, content, "\n");
 
     while (iterator.next()) |line| {
         const mutableSlice = try allocator.alloc(u8, line.len);