From 534ae9c20afb9b178a80bf807fe7e6e02dfd0cdf Mon Sep 17 00:00:00 2001
From: Sven Weidauer <sven@5sw.de>
Date: Sat, 11 Dec 2021 23:55:58 +0100
Subject: [PATCH] Day 11

---
 day11.swift | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 day11.swift

diff --git a/day11.swift b/day11.swift
new file mode 100644
index 0000000..2d16909
--- /dev/null
+++ b/day11.swift
@@ -0,0 +1,70 @@
+
+struct Day11 {
+    mutating func run() {
+        var count = 0
+        var currentStep = 0
+        repeat {
+            let stepCount = step()
+            count += stepCount
+            currentStep += 1
+            if (currentStep == 100) {
+                print("Part 1:", count)
+            }
+
+            if stepCount == width * height {
+                print("Part 2:", currentStep)
+                break
+            }
+        } while true
+    }
+
+    subscript(x: Int, y: Int) -> Int {
+        get { data[x + width * y] }
+        set { data[x + width * y] = newValue }
+    }
+
+    mutating func step() -> Int {
+        var flashes: Set<Point> = []
+
+        func up(x: Int, y: Int) {
+            self[x, y] += 1
+            if self[x, y] > 9, flashes.insert(Point(x: x, y: y)).inserted {
+                for i in -1...1 where 0..<height ~= y + i {
+                    for j in -1...1 where (i != 0 || j != 0) && 0..<width ~= x + j {
+                        up(x: x + j, y: y + i)
+                    }
+                }
+            }
+        }
+
+        for y in 0..<height {
+            for x in 0..<width {
+                up(x: x, y: y)
+            }
+        }
+
+        for point in flashes {
+            self[point.x, point.y] = 0
+        }
+
+        return flashes.count
+    }
+
+    struct Point: Hashable { var x: Int, y: Int }
+
+    let width = 10
+    let height = 10
+
+    var data = [
+        2, 5, 2, 4, 2, 5, 5, 3, 3, 1,
+        1, 1, 3, 5, 6, 2, 5, 8, 8, 1,
+        2, 8, 3, 8, 3, 5, 3, 8, 6, 3,
+        1, 6, 6, 2, 3, 1, 2, 3, 6, 5,
+        6, 8, 4, 7, 8, 3, 5, 8, 2, 5,
+        2, 1, 8, 5, 6, 8, 4, 3, 6, 7,
+        6, 8, 7, 4, 2, 1, 2, 8, 3, 1,
+        5, 3, 8, 7, 2, 4, 7, 8, 1, 1,
+        2, 2, 5, 5, 4, 8, 2, 8, 7, 5,
+        8, 5, 2, 8, 5, 5, 7, 1, 3, 1,
+    ]
+}