From 7fa8c31b11564ce77fcc3a292e5cb0291208bebc Mon Sep 17 00:00:00 2001
From: Patrick Michl <huanzodev@gmail.com>
Date: Tue, 22 Dec 2020 15:34:34 +0100
Subject: [PATCH] Solution for Day 22

---
 day_22/first.rb  | 15 ++++++++++++++
 day_22/input     | 53 ++++++++++++++++++++++++++++++++++++++++++++++++
 day_22/second.rb | 29 ++++++++++++++++++++++++++
 day_22/test      | 13 ++++++++++++
 4 files changed, 110 insertions(+)
 create mode 100644 day_22/first.rb
 create mode 100644 day_22/input
 create mode 100644 day_22/second.rb
 create mode 100644 day_22/test

diff --git a/day_22/first.rb b/day_22/first.rb
new file mode 100644
index 0000000..cd830b6
--- /dev/null
+++ b/day_22/first.rb
@@ -0,0 +1,15 @@
+input = File.read('./input').split("\n\n").map { |l| l.split("\n") }
+
+$p1 = input[0].drop(1).map(&:to_i)
+$p2 = input[1].drop(1).map(&:to_i)
+
+until $p1.empty? || $p2.empty?
+  p1 = $p1.shift
+  p2 = $p2.shift
+
+  p1 > p2 ? $p1.push(p1, p2) : $p2.push(p2, p1)
+end
+
+$winner = $p1.empty? ? $p2 : $p1
+
+puts (1..$winner.size).reverse_each.zip($winner).map { |l, r| l * r }.sum
diff --git a/day_22/input b/day_22/input
new file mode 100644
index 0000000..47ddfee
--- /dev/null
+++ b/day_22/input
@@ -0,0 +1,53 @@
+Player 1:
+28
+13
+25
+16
+38
+3
+14
+6
+29
+2
+47
+20
+35
+43
+30
+39
+21
+42
+50
+48
+23
+11
+34
+24
+41
+
+Player 2:
+27
+37
+9
+10
+17
+31
+19
+33
+40
+12
+32
+1
+18
+36
+49
+46
+26
+4
+45
+8
+15
+5
+44
+22
+7
diff --git a/day_22/second.rb b/day_22/second.rb
new file mode 100644
index 0000000..3ae2bcb
--- /dev/null
+++ b/day_22/second.rb
@@ -0,0 +1,29 @@
+input = File.read('./input').split("\n\n").map { |l| l.split("\n") }
+
+p1 = input[0].drop(1).map(&:to_i)
+p2 = input[1].drop(1).map(&:to_i)
+
+def play_game(deck1, deck2)
+  history = {}
+
+  until deck1.empty? || deck2.empty?
+    return true if history[deck1] && history[deck2]
+
+    history[deck1] = true
+    history[deck2] = true
+    p1 = deck1.shift
+    p2 = deck2.shift
+
+    round_winner = if p1 <= deck1.size && p2 <= deck2.size
+                     play_game(deck1[0, p1], deck2[0, p2])
+                   else
+                     p1 > p2
+                   end
+    round_winner ? deck1.push(p1, p2) : deck2.push(p2, p1)
+  end
+  winner = deck1.empty? ? deck2 : deck1
+  deck1.size > deck2.size
+end
+
+winner = play_game(p1, p2) ? p1 : p2
+puts (1..winner.size).reverse_each.zip(winner).map { |l, r| l * r }.sum
diff --git a/day_22/test b/day_22/test
new file mode 100644
index 0000000..dfaf6f7
--- /dev/null
+++ b/day_22/test
@@ -0,0 +1,13 @@
+Player1:
+9
+2
+6
+3
+1
+
+Player2:
+5
+8
+4
+7
+10