From 81562d744133eb5d3d2654f8e2c4a1f36b8ad2a6 Mon Sep 17 00:00:00 2001
From: Stefan Harmuth <stefan.harmuth@net-m.de>
Date: Thu, 31 Dec 2020 10:37:23 +0100
Subject: [PATCH] day20

---
 day20/day.go   | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++
 inputs/20      |  1 +
 inputs/20_test |  1 +
 main.go        |  2 ++
 4 files changed, 58 insertions(+)
 create mode 100644 day20/day.go
 create mode 100644 inputs/20
 create mode 100644 inputs/20_test

diff --git a/day20/day.go b/day20/day.go
new file mode 100644
index 0000000..e42fa68
--- /dev/null
+++ b/day20/day.go
@@ -0,0 +1,54 @@
+package day20
+
+import (
+	"math"
+	"tools"
+)
+
+func Part1(puzzle tools.AoCPuzzle) interface{} {
+	target := puzzle.GetInputArrayInt()[0]
+
+	presents := 0
+	houseNumber := 0
+	for presents < target {
+		houseNumber++
+		divisor := tools.NewSet()
+		for i := 1; i <= int(math.Sqrt(float64(houseNumber))); i++ {
+			if houseNumber%i == 0 {
+				divisor.Add(i)
+				divisor.Add(houseNumber / i)
+			}
+		}
+		presents = 0
+		for v := range divisor {
+			presents += v.(int) * 10
+		}
+	}
+
+	return houseNumber
+}
+
+func Part2(puzzle tools.AoCPuzzle) interface{} {
+	target := puzzle.GetInputArrayInt()[0]
+
+	presents := 0
+	houseNumber := 0
+	for presents < target {
+		houseNumber++
+		divisor := tools.NewSet()
+
+		for i := 1; i <= int(math.Sqrt(float64(houseNumber))); i++ {
+			if houseNumber%i == 0 {
+				divisor.Add(houseNumber / i)
+			}
+		}
+		presents = 0
+		for v := range divisor {
+			if houseNumber/v.(int) < 50 {
+				presents += v.(int) * 11
+			}
+		}
+	}
+
+	return houseNumber
+}
diff --git a/inputs/20 b/inputs/20
new file mode 100644
index 0000000..f1b40a7
--- /dev/null
+++ b/inputs/20
@@ -0,0 +1 @@
+34000000
\ No newline at end of file
diff --git a/inputs/20_test b/inputs/20_test
new file mode 100644
index 0000000..b6da794
--- /dev/null
+++ b/inputs/20_test
@@ -0,0 +1 @@
+4650
\ No newline at end of file
diff --git a/main.go b/main.go
index 36747d0..2d47c5b 100644
--- a/main.go
+++ b/main.go
@@ -20,6 +20,7 @@ import (
 	"aoc2015/day17"
 	"aoc2015/day18"
 	"aoc2015/day19"
+	"aoc2015/day20"
 	"flag"
 	"fmt"
 	"os"
@@ -56,6 +57,7 @@ func initDayFunctions() {
 		17: {1: day17.Part1, 2: day17.Part2},
 		18: {1: day18.Part1, 2: day18.Part2},
 		19: {1: day19.Part1, 2: day19.Part2},
+		20: {1: day20.Part1, 2: day20.Part2},
 	}
 }