1 files changed, 108 insertions, 0 deletions
diff --git a/day14.zig b/day14.zig
new file mode 100644
index 0000000..42f6b89
--- /dev/null
+++ b/day14.zig
@@ -0,0 +1,108 @@
+// needs -O ReleaseFast, else super slow
+
+const std = @import("std");
+const data = @embedFile("day14");
+
+var area = [_][800]u8{ [_]u8{0} ** 800 } ** 800;
+
+fn draw(ox: usize, oy: usize, x: usize, y: usize) void {
+    if (ox == x) {
+        var vy = std.math.min(oy, y);
+        while (vy <= std.math.max(oy, y)) : (vy += 1)
+            area[x][vy] = 9;
+    } else {
+        var vx = std.math.min(ox, x);
+        while (vx <= std.math.max(ox, x)) : (vx += 1)
+            area[vx][y] = 9;
+    }
+}
+
+fn drop_sand(y1: usize, x1: usize) bool {
+    var y = y1;
+    var x = x1;
+
+    while (x < 799 and y < 799) {
+        if (area[y+1][x] == 0) {
+            y += 1;
+            continue;
+        } 
+        if (area[y+1][x-1] == 0) {
+            x -= 1;
+            y += 1;
+            continue;
+        }
+        if (area[y+1][x+1] == 0) {
+            x += 1;
+            y += 1;
+            continue;
+        }
+        area[y][x] = 1;
+        return true;
+    }
+    
+    return false;
+}
+
+pub fn main() !void {
+    var lines = std.mem.tokenize(u8, data, "\n");
+
+    while (lines.next()) |line| {
+        if (line.len == 0)
+            break;
+
+        var coords = std.mem.tokenize(u8, line, " -> ");
+
+        var ox: usize = 0;
+        var oy: usize = 0;
+        while (coords.next()) |coord| {
+            var ns = std.mem.tokenize(u8, coord, ",");
+            var y = try std.fmt.parseInt(usize, ns.next().?, 10);
+            var x = try std.fmt.parseInt(usize, ns.next().?, 10);
+
+            if (ox != 0)
+                draw(ox, oy, x, y);
+
+            ox = x;
+            oy = y;
+        }
+    }
+
+
+    var part1: usize = 0;
+    while (drop_sand(0, 500))
+        part1 += 1;
+
+    for (area) |*line| {
+        for (line) |*item| {
+            if (item.* == 1)
+                item.* = 0;
+        }
+    }
+
+    var bottom: usize = 799;
+    loop: while (bottom > 0) : (bottom -= 1) {
+        for (area[bottom]) |item| {
+            if (item == 9) {
+                draw(bottom + 2, 0, bottom + 2, 799);
+                break :loop;
+            }
+        }
+    }
+    
+    var part2: usize = 0;
+    loop: while (drop_sand(0, 500)) {
+        part2 += 1;
+
+        if (area[0][500] != 0)
+            break :loop;
+    }
+
+//    for (area) |line| {
+//        for (line) |item| {
+//            std.debug.print("{}", .{item});
+//        }
+//        std.debug.print("\n", .{});
+//    }
+
+    std.debug.print("{}\n{}\n", .{part1, part2});
+}