From df3ee0e171b6402c1fa407ea090fe7d2ff2563eb Mon Sep 17 00:00:00 2001
From: ptrcnull <git@ptrcnull.me>
Date: Sun, 12 Dec 2021 10:58:43 +0100
Subject: [PATCH] 11: part1+2

---
 11/input     |  10 +++++
 11/solve.zig | 115 +++++++++++++++++++++++++++++++++++++++++++++++++++
 11/testinput |  10 +++++
 3 files changed, 135 insertions(+)
 create mode 100644 11/input
 create mode 100644 11/solve.zig
 create mode 100644 11/testinput

diff --git a/11/input b/11/input
new file mode 100644
index 0000000..ed7ceb3
--- /dev/null
+++ b/11/input
@@ -0,0 +1,10 @@
+2138862165
+2726378448
+3235172758
+6281242643
+4256223158
+1112268142
+1162836182
+1543525861
+1882656326
+8844263151
diff --git a/11/solve.zig b/11/solve.zig
new file mode 100644
index 0000000..6da1acc
--- /dev/null
+++ b/11/solve.zig
@@ -0,0 +1,115 @@
+const std = @import("std");
+const print = std.debug.print;
+
+const matrixSize = 10;
+const iterations = std.math.maxInt(u32);
+// const iterations = 100;
+// const iterations = 10;
+
+const Point = [2]usize;
+
+const NeighborList = struct {
+    fn init(alloc: *std.mem.Allocator, x: usize, y: usize) std.ArrayList(Point) {
+        var list = std.ArrayList(Point).init(alloc);
+
+        for ([_]i8{-1, 0, 1}) |a| {
+            var _x = @intCast(i8, x & 0xf) + a;
+            if (_x < 0 or _x >= matrixSize) continue;
+
+            for ([_]i8{-1, 0, 1}) |b| {
+                var _y = @intCast(i8, y & 0xf) + b;
+                if (_y < 0 or _y >= matrixSize) continue;
+                if (a == 0 and b == 0) continue;
+
+                list.append(Point{@intCast(usize, _x), @intCast(usize, _y)}) catch {};
+            }
+        }
+
+        return list;
+    }
+};
+
+pub fn main() !void {
+    var alloc = std.heap.GeneralPurposeAllocator(.{}){};
+    defer std.debug.assert(!alloc.deinit());
+    var gpa = &alloc.allocator;
+
+    const stdin = std.io.getStdIn().reader();
+
+    var flashes: u32 = 0;
+    var fullFlashStep: u32 = 0;
+
+    var matrix: [matrixSize][matrixSize]u8 = undefined;
+
+    // parse data
+    {
+        var tmp: [256]u8 = undefined;
+        var i: u8 = 0;
+        while (try stdin.readUntilDelimiterOrEof(&tmp, '\n')) |line| {
+            for (line) |char, j| {
+                matrix[i][j] = char - 0x30;
+            }
+
+            i += 1;
+        }
+    }
+
+    var i: u32 = 0;
+    while (i < iterations) : (i += 1) {
+        // print("iteration {}\n", .{i});
+
+        var flashed: [matrixSize][matrixSize]bool = undefined;
+
+        for (matrix) |row, x| {
+            for (row) |_, y| {
+                matrix[x][y] += 1;
+            }
+        }
+
+        while (true) {
+            var retry = false;
+
+            for (matrix) |row, x| {
+                for (row) |tile, y| {
+                    if (matrix[x][y] > 9 and !flashed[x][y]) {
+                        flashed[x][y] = true;
+                        retry = true;
+
+                        if (i < 100) flashes += 1;
+
+                        var neigh = NeighborList.init(gpa, x, y);
+                        defer neigh.deinit();
+
+                        for (neigh.items) |point| {
+                            matrix[point[0]][point[1]] += 1;
+                        }
+                    }
+                }
+            }
+
+            if (!retry) break;
+        }
+
+        var numFlashed: u8 = 0;
+        for (flashed) |row, x| {
+            for (row) |hasFlashed, y| {
+                if (hasFlashed) {
+                    matrix[x][y] = 0;
+                    numFlashed += 1;
+                }
+            }
+        }
+
+        if (numFlashed == comptime matrixSize * matrixSize) {
+            fullFlashStep = i + 1;
+            break;
+        }
+
+        // for (matrix) |row| {
+        //     print("{any}\n", .{row});
+        // }
+    }
+
+    print("{}\n", .{flashes});
+    print("{}\n", .{fullFlashStep});
+}
diff --git a/11/testinput b/11/testinput
new file mode 100644
index 0000000..a3819c9
--- /dev/null
+++ b/11/testinput
@@ -0,0 +1,10 @@
+5483143223
+2745854711
+5264556173
+6141336146
+6357385478
+4167524645
+2176841721
+6882881134
+4846848554
+5283751526
\ No newline at end of file