Day 12, part1 only

1 files changed, 69 insertions, 0 deletions

diff --git a/day12/part1 b/day12/part1
new file mode 100755
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+++ b/day12/part1
@@ -0,0 +1,69 @@
+#!/usr/bin/env ruby
+
+input = $stdin.readlines.map(&:strip)
+
+is = input[0].split(" ")[2]
+rs = input[2..-1]
+
+class Plants
+  def initialize(initial_state, rules)
+    @state = Hash.new(false)
+    parse_state_string(initial_state)
+    @rules = []
+    parse_rules_lines(rules)
+  end
+
+  def step(t = 1)
+    t.times do
+      newstate = Hash.new(false)
+
+      min = @state.keys.min
+      max = @state.keys.max
+      ((min-5)..(max+5)).each do |i|
+        res = false
+        @rules.each do |r|
+          ires = true
+          (-2..2).each do |o|
+            if @state[i + o] != r[o + 2] then
+              ires = false
+            end
+          end
+          if ires then
+            res = true
+          end
+        end
+        if res then
+          newstate[i] = true
+        end
+      end
+
+      @state = newstate
+    end
+  end
+
+  def sum
+    @state.select { |_, s| s }.keys.sum
+  end
+
+  private
+  def parse_state_string(state)
+    state.chars.each_with_index do |s, i|
+      @state[i] = s == "#"
+    end
+  end
+
+  def parse_rules_lines(rules)
+    rules.each do |rule|
+      c, r = rule.split(" => ")
+      if r == "#" then
+        @rules << c.chars.map { |p| p == "#" }
+      end
+    end
+  end
+end
+
+m = Plants.new(is, rs)
+
+m.step(20)
+
+puts m.sum