From 602bc416d8ebf22d79fe21291c4ed5b0bb7066f1 Mon Sep 17 00:00:00 2001
From: Felix Van der Jeugt <felix.vanderjeugt@posteo.net>
Date: Tue, 7 Dec 2021 08:29:45 +0100
Subject: [PATCH] day 7

---
 day06/part1.lua |  0
 day06/part2.lua |  0
 day07/part1.lua | 14 ++++++++++++++
 day07/part2.lua | 28 ++++++++++++++++++++++++++++
 utils.lua       |  6 ++++++
 5 files changed, 48 insertions(+)
 mode change 100644 => 100755 day06/part1.lua
 mode change 100644 => 100755 day06/part2.lua
 create mode 100755 day07/part1.lua
 create mode 100755 day07/part2.lua

diff --git a/day06/part1.lua b/day06/part1.lua
old mode 100644
new mode 100755
diff --git a/day06/part2.lua b/day06/part2.lua
old mode 100644
new mode 100755
diff --git a/day07/part1.lua b/day07/part1.lua
new file mode 100755
index 0000000..b89ca18
--- /dev/null
+++ b/day07/part1.lua
@@ -0,0 +1,14 @@
+#!/usr/bin/env luajit
+require("utils")
+
+local positions = split(io.open(arg[3]):read("*a"), ",")
+foreach(positions, tonumber)
+table.sort(positions)
+
+local median = positions[#positions/2]
+local cost = 0
+for k, v in pairs(positions) do
+	cost = cost + math.abs(median - v)
+end
+
+print(cost)
diff --git a/day07/part2.lua b/day07/part2.lua
new file mode 100755
index 0000000..2931546
--- /dev/null
+++ b/day07/part2.lua
@@ -0,0 +1,28 @@
+#!/usr/bin/env luajit
+require("utils")
+
+local positions = split(io.open(arg[3]):read("*a"), ",")
+foreach(positions, tonumber)
+
+local min, max = math.huge, -math.huge
+for k, v in pairs(positions) do
+	if v < min then min = v end
+	if v > max then max = v end
+end
+
+function gauss(n)
+	return n * (n + 1) / 2
+end
+
+local minimum = math.huge
+for i = min, max do
+	local cost = 0
+	for k, v in pairs(positions) do
+		cost = cost + gauss(math.abs(i - v))
+	end
+	if cost < minimum then
+		minimum = cost
+	end
+end
+
+print(minimum)
diff --git a/utils.lua b/utils.lua
index 94439b9..4e32290 100644
--- a/utils.lua
+++ b/utils.lua
@@ -17,3 +17,9 @@ function sign(n)
 	else return 1
 	end
 end
+
+function foreach(t, f)
+	for k, v in pairs(t) do
+		t[k] = f(v)
+	end
+end