From 69a8c7bb9862966b2f21dbb61e86f652f9b238f9 Mon Sep 17 00:00:00 2001
From: Marcin Chrzanowski <marcin.j.chrzanowski@gmail.com>
Date: Fri, 25 Dec 2020 15:27:26 +0100
Subject: Add day 11

---
 11/b.rb | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 11/b.rb

(limited to '11/b.rb')

diff --git a/11/b.rb b/11/b.rb
new file mode 100644
index 0000000..bc93bce
--- /dev/null
+++ b/11/b.rb
@@ -0,0 +1,58 @@
+input = File.readlines('input.txt').map { |l| ".#{l.chomp}.".split '' }
+input.unshift(['.'] * input[0].length)
+input.push(['.'] * input[0].length)
+
+next_map = []
+input.size.times do
+  row = []
+  input[0].size.times do
+    row.push '.'
+  end
+  next_map.push row
+end
+
+changed = true
+current_count = 0
+while changed
+  current_count = 0
+  changed = false
+  (1...input.length-1).each do |i|
+    (1...input[0].length-1).each do |j|
+      if input[i][j] != '.'
+        count = 0
+        (-1..1).each do |di|
+          (-1..1).each do |dj|
+            if !(di == 0 && dj == 0)
+              offset_i = i + di
+              offset_j = j + dj
+              while offset_i > 0 && offset_i < input.length - 1 && offset_j > 0 && offset_j < input[0].length - 1 && input[offset_i][offset_j] == '.'
+                offset_i += di
+                offset_j += dj 
+              end
+
+              count += input[offset_i][offset_j] == '#' ? 1 : 0
+            end
+          end
+        end
+      
+        if count == 0 && input[i][j] == 'L'
+          next_map[i][j] = '#'
+          changed = true
+        elsif count >= 5 && input[i][j] == '#'
+          next_map[i][j] = 'L'
+          changed = true
+        else
+          next_map[i][j] = input[i][j]
+        end
+
+        current_count += next_map[i][j] == '#' ? 1 : 0
+      end
+    end
+  end
+
+  tmp = input
+  input = next_map
+  next_map = tmp
+end
+
+puts current_count
-- 
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