Vectors!

src/days/day09.zig

@@ -30,7 +30,7 @@ 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, .{ .x = x, .y = y });
+        try tiles.append(allocator, .{ .pos = .{ x, y } });
     }
 
     var largest_area: usize = 0;
@@ -58,13 +58,12 @@ pub fn run(allocator: std.mem.Allocator) !void {
 }
 
 const Tile = struct {
-    x: u64,
-    y: u64,
+    pos: @Vector(2, u64),
 
     const Self = @This();
 
     pub fn format(self: Self, w: *std.io.Writer) std.io.Writer.Error!void {
-        try w.print("{d},{d}", .{self.x, self.y});
+        try w.print("{d},{d}", .{self.pos[0], self.pos[1]});
     }
 
     pub fn rectangle(self: Self, other_corner: Self) Rectangle {
@@ -83,9 +82,12 @@ const Rectangle = struct {
     }
 
     pub fn area(self: Self) u64 {
-        const width = @max(self.a.x, self.b.x) - @min(self.a.x, self.b.x) + 1;
-        const height = @max(self.a.y, self.b.y) - @min(self.a.y, self.b.y) + 1;
-        return width * height;
+        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;
+        const one: @Vector(2, u64) = @splat(1);
+        return @reduce(.Mul, diff + one);
     }
 };