From 0df6aa12fd433f7fefc5302f712c3060615cda0f Mon Sep 17 00:00:00 2001
From: Marcin Chrzanowski <marcin.j.chrzanowski@gmail.com>
Date: Fri, 25 Dec 2020 15:49:44 +0100
Subject: Add day 22

---
 22/a.lua     | 40 +++++++++++++++++++++++++++++
 22/b.lua     | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 22/input.txt | 53 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 176 insertions(+)
 create mode 100644 22/a.lua
 create mode 100644 22/b.lua
 create mode 100644 22/input.txt

diff --git a/22/a.lua b/22/a.lua
new file mode 100644
index 0000000..50cd196
--- /dev/null
+++ b/22/a.lua
@@ -0,0 +1,40 @@
+deck1 = {}
+file = io.open('input.txt')
+for line in file:lines() do
+    if line:find('%d+') then
+        table.insert(deck1, tonumber(line))
+    elseif line == '' then
+        break
+    end
+end
+deck2 = {}
+for line in file:lines() do
+    if line:find('%d+') then
+        table.insert(deck2, tonumber(line))
+    end
+end
+
+ended = false
+
+while #deck1 > 0 and #deck2 > 0 do
+    card1 = table.remove(deck1, 1)
+    card2 = table.remove(deck2, 1)
+    if card1 > card2 then
+        table.insert(deck1, card1)
+        table.insert(deck1, card2)
+    else
+        table.insert(deck2, card2)
+        table.insert(deck2, card1)
+    end
+end
+
+deck = deck1
+if #deck1 == 0 then
+    deck = deck2
+end
+
+score = 0
+for i = 1, #deck do
+    score = score + i * (deck[#deck - i + 1]) 
+end
+print(score)
diff --git a/22/b.lua b/22/b.lua
new file mode 100644
index 0000000..ed6e862
--- /dev/null
+++ b/22/b.lua
@@ -0,0 +1,83 @@
+deck1 = {}
+file = io.open('input.txt')
+for line in file:lines() do
+    if line:find('%d+') then
+        table.insert(deck1, tonumber(line))
+    elseif line == '' then
+        break
+    end
+end
+deck2 = {}
+for line in file:lines() do
+    if line:find('%d+') then
+        table.insert(deck2, tonumber(line))
+    end
+end
+
+function make_signature(deck1, deck2)
+    return table.concat(deck1, ',') .. '#' .. table.concat(deck2, ',')
+end
+
+function copy(deck, n)
+    local new_deck = {}
+    for i = 1, n do
+        table.insert(new_deck, deck[i])
+    end
+    return new_deck
+end
+
+function play_game(deck1, deck2, calculate_score)
+    local winner = nil
+    local previous_rounds = {}
+
+    while not winner do
+        if not previous_rounds[make_signature(deck1, deck2)] then
+            previous_rounds[make_signature(deck1, deck2)] = true
+            local card1 = table.remove(deck1, 1)
+            local card2 = table.remove(deck2, 1)
+            local one_won_round = true
+            if card1 <= #deck1 and card2 <= #deck2 then
+                one_won_round = play_game(copy(deck1, card1), copy(deck2, card2), false)
+            else
+                one_won_round = card1 > card2
+            end
+            if one_won_round then
+                table.insert(deck1, card1)
+                table.insert(deck1, card2)
+            else
+                table.insert(deck2, card2)
+                table.insert(deck2, card1)
+            end
+
+            if #deck2 == 0 then
+                winner = 1
+            elseif #deck1 == 0 then
+                winner = 2
+            end
+        else
+            winner = 1
+        end
+    end
+
+    if calculate_score then
+        deck = deck1
+        if winner == 2 then
+            deck = deck2
+        end
+
+        score = 0
+        for i = 1, #deck do
+            score = score + i * (deck[#deck - i + 1]) 
+        end
+
+        return score
+    end
+
+    if winner == 1 then
+        return true
+    else
+        return false
+    end
+end
+
+print(play_game(deck1, deck2, true))
diff --git a/22/input.txt b/22/input.txt
new file mode 100644
index 0000000..62dc0e5
--- /dev/null
+++ b/22/input.txt
@@ -0,0 +1,53 @@
+Player 1:
+29
+21
+38
+30
+25
+7
+2
+36
+16
+44
+20
+12
+45
+4
+31
+34
+33
+42
+50
+14
+39
+37
+11
+43
+18
+
+Player 2:
+32
+24
+10
+41
+13
+3
+6
+5
+9
+8
+48
+49
+46
+17
+22
+35
+1
+19
+23
+28
+40
+26
+47
+15
+27
-- 
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