WIP: implement part 2

src/days/day09.zig

@@ -3,24 +3,26 @@ const std = @import("std");
 pub const title = "Day 09: Movie Theater";
 
 pub fn run(allocator: std.mem.Allocator) !void {
-    const input = @embedFile("./input/day09.txt");
-    //const input =
-    //    \\7,1
-    //    \\11,1
-    //    \\11,7
-    //    \\9,7
-    //    \\9,5
-    //    \\2,5
-    //    \\2,3
-    //    \\7,3
-    //    ;
+    //const input = @embedFile("./input/day09.txt");
+    const input =
+        \\7,1
+        \\11,1
+        \\11,7
+        \\9,7
+        \\9,5
+        \\2,5
+        \\2,3
+        \\7,3
+        ;
 
     var lines = std.mem.tokenizeScalar(u8, input, '\n');
 
     var tiles: std.ArrayList(Tile) = .empty;
     defer tiles.deinit(allocator);
 
+    var index: usize = 0;
     while (lines.next()) |line| {
+        defer index += 1;
         var coordinates = std.mem.tokenizeScalar(u8, line, ',');
         const x = blk: {
             const s = coordinates.next() orelse continue;
@@ -30,20 +32,53 @@ pub fn run(allocator: std.mem.Allocator) !void {
             const s = coordinates.next() orelse continue;
             break :blk try std.fmt.parseUnsigned(u64, s, 10);
         };
-        try tiles.append(allocator, .{ .pos = .{ x, y } });
+        try tiles.append(allocator, .{ .index = index, .pos = .{ x, y } });
+    }
+
+    const width = 14;
+    const height = 9;
+    for (0..height) |y| {
+        var buffer: [width]u8 = [_]u8{'.'} ** width;
+        for (0..width) |x| {
+            for (tiles.items) |tile| {
+                if (@reduce(.And, tile.pos == @Vector(2, u64){ x, y })) {
+                    buffer[x] = 'X';
+                }
+            }
+        }
+        std.debug.print("{s}\n", .{buffer});
     }
 
     var largest_area: usize = 0;
     var largest_rectangle: Rectangle = undefined;
     for (tiles.items, 0..) |first_tile, i| {
+        if (i == 0) continue;
         for (tiles.items[i + 1..]) |second_tile| {
             const rectangle = first_tile.rectangle(second_tile);
+            const w = rectangle.width();
+            const h = rectangle.height();
+            std.debug.print("rectangle {d}-{d}\n", .{rectangle.a.index, rectangle.b.index});
+            std.debug.print("width = {d}, height = {d}\n", .{w, h});
+
+            if (w != 1 and h != 1) {
+                var verts_outside: bool = false;
+                for (tiles.items[first_tile.index + 1..second_tile.index]) |between| {
+                    const cond = rectangle.c > between.pos;
+                    if (@reduce(.Or, cond)) {
+                        std.debug.print("vert c ({any}) of rect {d}-{d} is outside the shape\n", .{rectangle.c, rectangle.a.index, rectangle.b.index});
+                        verts_outside = true;
+                        break;
+                    }
+                }
+            }
+
             const area = rectangle.area();
             if (area > largest_area) {
                 largest_area = area;
                 largest_rectangle = rectangle;
             }
         }
+        break;
     }
 
     std.debug.print("rectangle = {f}\n", .{largest_rectangle});
@@ -58,6 +93,7 @@ pub fn run(allocator: std.mem.Allocator) !void {
 }
 
 const Tile = struct {
+    index: usize,
     pos: @Vector(2, u64),
 
     const Self = @This();
@@ -67,20 +103,52 @@ const Tile = struct {
     }
 
     pub fn rectangle(self: Self, other_corner: Self) Rectangle {
-        return .{ .a = self, .b = other_corner };
+        const a = self;
+        const b = other_corner;
+        return .{
+            .a = a,
+            .b = b,
+            .c = .{ b.pos[0], a.pos[1] },
+            .d = .{ a.pos[0], b.pos[1] },
+        };
     }
 };
 
+/// 0,0    1,0
+///  a ---- c
+///  |      |
+///  |      |
+///  d ---- b
+/// 0,1    1,1
 const Rectangle = struct {
     a: Tile,
     b: Tile,
 
+    c: @Vector(2, u64),
+    d: @Vector(2, u64),
+
     const Self = @This();
 
     pub fn format(self: Self, w: *std.io.Writer) std.io.Writer.Error!void {
         try w.print("{f} to {f}", .{self.a, self.b});
     }
 
+    pub fn width(self: Self) u64 {
+        const cond = self.a.pos > self.b.pos;
+        const high = @select(u64, cond, self.a.pos, self.b.pos);
+        const low = @select(u64, !cond, self.a.pos, self.b.pos);
+        const diff = high - low;
+        return diff[0] + 1;
+    }
+
+    pub fn height(self: Self) u64 {
+        const cond = self.a.pos > self.b.pos;
+        const high = @select(u64, cond, self.a.pos, self.b.pos);
+        const low = @select(u64, !cond, self.a.pos, self.b.pos);
+        const diff = high - low;
+        return diff[1] + 1;
+    }
+
     pub fn area(self: Self) u64 {
         const cond = self.a.pos > self.b.pos;
         const high = @select(u64, cond, self.a.pos, self.b.pos);