From 91fbd98401dcde40c483cad42b746115d133bbd1 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <Nat Lasseter nathan@bytemark.co.uk>
Date: Mon, 11 Dec 2017 10:40:38 +0000
Subject: Day 11

---
 day11/part1 | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100755 day11/part1

(limited to 'day11/part1')

diff --git a/day11/part1 b/day11/part1
new file mode 100755
index 0000000..372fb71
--- /dev/null
+++ b/day11/part1
@@ -0,0 +1,63 @@
+#!/usr/bin/env ruby
+
+def optimise_ortho_meta(loc, left, right, center)
+  opt = [loc[left], loc[right]].min
+  loc[left] -= opt
+  loc[right] -= opt
+  loc[center] += opt
+  return opt > 0
+end
+
+def optimise_para(loc, forth, back)
+  return false if loc[forth].zero? || loc[back].zero?
+
+  if loc[forth] > loc[back] then
+    loc[forth] = loc[forth] - loc[back]
+    loc[back] = 0
+    return true
+  end
+
+  if loc[back] > loc[forth] then
+    loc[back] = loc[back] - loc[forth]
+    loc[forth] = 0
+    return true
+  end
+
+  loc[forth] = 0
+  loc[back] = 0
+  return true
+end
+
+input = gets.chomp.split(',')
+
+l = {
+  n:  0,
+  ne: 0,
+  se: 0,
+  s:  0,
+  sw: 0,
+  nw: 0
+}
+
+input.each do |dir|
+  l[dir.intern] += 1
+end
+
+changed = true
+while changed do
+  changed = false
+
+  changed |= optimise_ortho_meta(l, :ne, :nw, :n)
+  changed |= optimise_ortho_meta(l, :se, :sw, :s)
+
+  changed |= optimise_ortho_meta(l, :n, :se, :ne)
+  changed |= optimise_ortho_meta(l, :n, :sw, :nw)
+  changed |= optimise_ortho_meta(l, :s, :ne, :se)
+  changed |= optimise_ortho_meta(l, :s, :nw, :sw)
+
+  changed |= optimise_para(l, :nw, :se)
+  changed |= optimise_para(l, :n, :s)
+  changed |= optimise_para(l, :ne, :sw)
+end
+
+puts l.values.inject(:+)
-- 
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