From 92d37d76344814787fafd492defaa96442bc546a Mon Sep 17 00:00:00 2001
From: Rickard Natt och Dag <rickard@nattochdag.dev>
Date: Sun, 22 Dec 2024 10:42:43 +0100
Subject: [PATCH] feat(2024): add day 22

---
 go/2024/README.md                          |  2 +
 go/2024/puzzles/day22/main.go              | 93 ++++++++++++++++++++++
 go/2024/puzzles/day22/main_test.go         | 35 ++++++++
 go/2024/puzzles/day22/test-input-part2.txt |  4 +
 go/2024/puzzles/day22/test-input.txt       |  4 +
 5 files changed, 138 insertions(+)
 create mode 100644 go/2024/puzzles/day22/main.go
 create mode 100644 go/2024/puzzles/day22/main_test.go
 create mode 100644 go/2024/puzzles/day22/test-input-part2.txt
 create mode 100644 go/2024/puzzles/day22/test-input.txt

diff --git a/go/2024/README.md b/go/2024/README.md
index 101c87c..88de12b 100644
--- a/go/2024/README.md
+++ b/go/2024/README.md
@@ -35,6 +35,7 @@ Collect stars by solving puzzles. Two puzzles will be made available on each day
 | [Day 19: Linen Layout](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day19/main.go)           | 🌟  |               209 | 🌟  | 777669668613191 |
 | [Day 20: Race Condition](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day20/main.go)         | 🌟  |              1351 | 🌟  |          966130 |
 | [Day 21: Keypad Conundrum](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day21/main.go)       | 🌟  |            217662 | 🌟  | 263617786809000 |
+| [Day 22: Monkey Market](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day22/main.go)          | 🌟  |       20068964552 | 🌟  |            2246 |
 
 ## Benchmarks
 
@@ -63,6 +64,7 @@ Using Go's built-in benchmarking with the [testing](https://pkg.go.dev/testing#h
 | 19  |  16126963 ns/op |   16206756 ns/op |                     |
 | 20  | 106801508 ns/op |  306290916 ns/op | `85.99%` / `63.78%` |
 | 21  |     16344 ns/op |      16282 ns/op |                     |
+| 22  |  36743155 ns/op |  617890208 ns/op |                     |
 
 \* compared to first solution
 
diff --git a/go/2024/puzzles/day22/main.go b/go/2024/puzzles/day22/main.go
new file mode 100644
index 0000000..ae5c207
--- /dev/null
+++ b/go/2024/puzzles/day22/main.go
@@ -0,0 +1,93 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/believer/aoc-2024/utils"
+	"github.com/believer/aoc-2024/utils/files"
+)
+
+func main() {
+	fmt.Println("Part 1: ", part1("input.txt"))
+	fmt.Println("Part 2: ", part2("input.txt"))
+}
+
+func part1(name string) (total int) {
+	buyers := files.ReadLines(name)
+
+	for _, buyer := range buyers {
+		secret := utils.MustIntFromString(buyer)
+
+		for range 2000 {
+			secret = generateSecret(secret)
+		}
+
+		total += secret
+	}
+
+	return total
+}
+
+type Pattern [4]int
+
+func part2(name string) (maxBananas int) {
+	buyers := files.ReadLines(name)
+	scores := map[Pattern]int{}
+
+	for _, buyer := range buyers {
+		secret := utils.MustIntFromString(buyer)
+		patterns := [][2]int{}
+		seen := map[Pattern]bool{}
+		last := secret % 10
+
+		// Generate all secrets and their deltas
+		for range 2000 {
+			secret = generateSecret(secret)
+			temp := secret % 10
+			patterns = append(patterns, [2]int{temp - last, temp})
+			last = temp
+		}
+
+		// Go through the patterns four by four and them to the total score
+		for i := range len(patterns) - 4 {
+			key := Pattern{
+				patterns[i][0],
+				patterns[i+1][0],
+				patterns[i+2][0],
+				patterns[i+3][0],
+			}
+
+			if _, ok := seen[key]; !ok {
+				seen[key] = true
+				scores[key] += patterns[i+3][1]
+			}
+		}
+	}
+
+	for _, b := range scores {
+		maxBananas = max(maxBananas, b)
+	}
+
+	return maxBananas
+}
+
+func generateSecret(secret int) int {
+	prune := 16777216
+
+	// Step 1
+	result := secret * 64
+	secret ^= result
+	secret %= prune
+
+	// Step 2
+	result = secret / 32
+	secret ^= result
+	secret %= prune
+
+	// Step 3
+	result = secret * 2048
+	secret ^= result
+	secret %= prune
+
+	return secret
+}
diff --git a/go/2024/puzzles/day22/main_test.go b/go/2024/puzzles/day22/main_test.go
new file mode 100644
index 0000000..ffe71d9
--- /dev/null
+++ b/go/2024/puzzles/day22/main_test.go
@@ -0,0 +1,35 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPart1(t *testing.T) {
+	t.Run("Part 1", func(t *testing.T) {
+		expected := 37327623
+		actual := part1("test-input.txt")
+		assert.Equal(t, expected, actual)
+	})
+}
+
+func TestPart2(t *testing.T) {
+	t.Run("Part 2", func(t *testing.T) {
+		expected := 23
+		actual := part2("test-input-part2.txt")
+		assert.Equal(t, expected, actual)
+	})
+}
+
+func BenchmarkPart1(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		part1("input.txt")
+	}
+}
+
+func BenchmarkPart2(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		part2("input.txt")
+	}
+}
diff --git a/go/2024/puzzles/day22/test-input-part2.txt b/go/2024/puzzles/day22/test-input-part2.txt
new file mode 100644
index 0000000..201df76
--- /dev/null
+++ b/go/2024/puzzles/day22/test-input-part2.txt
@@ -0,0 +1,4 @@
+1
+2
+3
+2024
diff --git a/go/2024/puzzles/day22/test-input.txt b/go/2024/puzzles/day22/test-input.txt
new file mode 100644
index 0000000..07b41ba
--- /dev/null
+++ b/go/2024/puzzles/day22/test-input.txt
@@ -0,0 +1,4 @@
+1
+10
+100
+2024