From d4b47d15a1a837c777c1f155d24d7c3ae111a7c5 Mon Sep 17 00:00:00 2001
From: Marcin Chrzanowski <marcin.j.chrzanowski@gmail.com>
Date: Fri, 25 Dec 2020 15:51:05 +0100
Subject: Add day 23

---
 23/a.lua | 63 +++++++++++++++++++++++++++++++++++++++++
 23/b.lua | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 162 insertions(+)
 create mode 100644 23/a.lua
 create mode 100644 23/b.lua

diff --git a/23/a.lua b/23/a.lua
new file mode 100644
index 0000000..811ccdc
--- /dev/null
+++ b/23/a.lua
@@ -0,0 +1,63 @@
+input = '716892543'
+cups = {}
+for i = 1, #input do
+    table.insert(cups, tonumber(input:sub(i,i)))
+end
+
+function next_target(n)
+    n = n - 1
+    if n == 0 then
+        n = 9
+    end
+    return n
+end
+
+for round = 1, 100 do
+    current_value = cups[1]
+
+    next_values = {}
+    for i = 2, 4 do
+        next_values[cups[i]] = true
+    end
+
+    target = next_target(current_value)
+    while next_values[target] do
+        target = next_target(target)
+    end
+
+    target_index = 5
+    while cups[target_index] ~= target do
+        target_index = target_index + 1
+    end
+
+    new_cups = {}
+    if target_index ~= 5 then
+        for i = 5, target_index - 1 do
+            table.insert(new_cups, cups[i])
+        end
+    end
+    table.insert(new_cups, target)
+    for i = 2, 4 do
+        table.insert(new_cups, cups[i])
+    end
+    if target_index ~= 9 then
+        for i = target_index + 1, 9 do
+            table.insert(new_cups, cups[i])
+        end
+    end
+    table.insert(new_cups, cups[1])
+    cups = new_cups
+end
+
+one_index = 1
+while cups[one_index] ~= 1 do
+    one_index = one_index + 1
+end
+
+for i = one_index + 1, 9 do
+    io.write(cups[i])
+end
+for i = 1, one_index - 1 do
+    io.write(cups[i])
+end
+print()
diff --git a/23/b.lua b/23/b.lua
new file mode 100644
index 0000000..6d504b0
--- /dev/null
+++ b/23/b.lua
@@ -0,0 +1,99 @@
+Node = {}
+Node.__index = Node
+function Node:new(value)
+    object = {}
+    object.value = value
+    object.right = nil
+    object.left = nil
+    return setmetatable(object, self)
+end
+
+function Node:insert(left)
+    self.left = left
+    self.right = left.right
+    self.right.left = self
+    self.left.right = self
+end
+
+function Node:detach()
+    self.left.right = self.right
+    self.right.left = self.left
+    self.left = nil
+    self.right = nil
+    return self
+end
+
+CyclicList = {}
+CyclicList.__index = CyclicList
+
+function CyclicList:new()
+    object = {}
+    object.head = nil
+    object.last = nil
+    object.index = {}
+    return setmetatable(object, self)
+end
+
+function CyclicList:insert(value)
+    node = Node:new(value)
+    self.index[value] = node
+    if self.head == nil then
+        self.head = node
+        node.left = node
+        node.right = node
+    else
+        node:insert(self.head.left)
+    end
+end
+
+function CyclicList:move_head(node)
+    self.head = node
+end
+
+input = '716892543'
+cups = CyclicList:new()
+for i = 1, #input do
+    cups:insert(tonumber(input:sub(i,i)))
+end
+for i = 10, 1000000 do
+    cups:insert(i)
+end
+
+function next_target(n)
+    n = n - 1
+    if n == 0 then
+        n = 1000000
+    end
+    return n
+end
+
+for round = 1, 10000000 do
+    current_value = cups.head.value
+
+    next_node = cups.head.right
+    next_values = {}
+    for i = 1, 3 do
+        next_values[next_node.value] = true
+        next_node = next_node.right
+    end
+
+    target = next_target(current_value)
+    while next_values[target] do
+        target = next_target(target)
+    end
+
+    target_node = cups.index[target]
+
+    for i = 1, 3 do
+        moved_node = cups.head.right:detach()
+        moved_node:insert(target_node)
+        target_node = moved_node
+    end
+
+    cups:move_head(cups.head.right)
+end
+
+one_node = cups.index[1]
+a = one_node.right.value
+b = one_node.right.right.value
+print(a * b)
-- 
cgit v1.2.3