From db70c7c603ab92237d098ea9c819638c9f1a7431 Mon Sep 17 00:00:00 2001
From: Tyler Beckman <ty@myriation.xyz>
Date: Sat, 21 Dec 2024 22:59:47 -0700
Subject: [PATCH] Day 22

---
 Cargo.toml     |  8 +++++++
 day22/part1.rs | 53 +++++++++++++++++++++++++++++++++++++++++
 day22/part2.rs | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 125 insertions(+)
 create mode 100644 day22/part1.rs
 create mode 100644 day22/part2.rs

diff --git a/Cargo.toml b/Cargo.toml
index e6bcd08..5f9958b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -51,3 +51,11 @@ path = "day20/part1.rs"
 [[bin]]
 name = "d20p2"
 path = "day20/part2.rs"
+
+[[bin]]
+name = "d22p1"
+path = "day22/part1.rs"
+
+[[bin]]
+name = "d22p2"
+path = "day22/part2.rs"
diff --git a/day22/part1.rs b/day22/part1.rs
new file mode 100644
index 0000000..7bb9f5d
--- /dev/null
+++ b/day22/part1.rs
@@ -0,0 +1,53 @@
+#![feature(const_str_split_at)]
+const INPUT_LINES: usize = {
+    let bytes = include_bytes!("input.txt");
+    let mut i = 0;
+    let mut count = 0;
+    while i < bytes.len() {
+        if bytes[i] == b'\n' {
+            count += 1;
+        }
+        i += 1;
+    }
+
+    count
+};
+const INPUT: [u128; INPUT_LINES] = {
+    let data = include_str!("input.txt");
+    let mut nums = [0; INPUT_LINES];
+
+    let mut i = 0;
+    let mut count = 0;
+    let mut last_newline = 0;
+    while i < data.len() {
+        if data.as_bytes()[i] == b'\n' {
+            let Ok(parsed) = u128::from_str_radix(data.split_at(last_newline).1.split_at(i - last_newline).0.trim_ascii(), 10) else {
+                panic!();
+            };
+            nums[count] = parsed;
+            count += 1;
+            last_newline = i;
+        }
+        i += 1;
+    }
+
+    nums
+};
+
+fn main() {
+    let mut sum = 0u128;
+    for mut secret in INPUT {
+        for _ in 0..2000 {
+            secret ^= secret * 64;
+            secret %= 16777216;
+            secret ^= secret / 32;
+            secret %= 16777216;
+            secret ^= secret * 2048;
+            secret %= 16777216;
+        }
+
+        sum += secret;
+    }
+
+    println!("Result: {sum}");
+}
diff --git a/day22/part2.rs b/day22/part2.rs
new file mode 100644
index 0000000..a206777
--- /dev/null
+++ b/day22/part2.rs
@@ -0,0 +1,64 @@
+#![feature(const_str_split_at)]
+
+use std::collections::{HashMap, HashSet};
+const INPUT_LINES: usize = {
+    let bytes = include_bytes!("input.txt");
+    let mut i = 0;
+    let mut count = 0;
+    while i < bytes.len() {
+        if bytes[i] == b'\n' {
+            count += 1;
+        }
+        i += 1;
+    }
+
+    count
+};
+const INPUT: [u64; INPUT_LINES] = {
+    let data = include_str!("input.txt");
+    let mut nums = [0; INPUT_LINES];
+
+    let mut i = 0;
+    let mut count = 0;
+    let mut last_newline = 0;
+    while i < data.len() {
+        if data.as_bytes()[i] == b'\n' {
+            let Ok(parsed) = u64::from_str_radix(data.split_at(last_newline).1.split_at(i - last_newline).0.trim_ascii(), 10) else {
+                panic!();
+            };
+            nums[count] = parsed;
+            count += 1;
+            last_newline = i;
+        }
+        i += 1;
+    }
+
+    nums
+};
+
+fn main() {
+    let mut sequences = HashMap::<[i8; 4], u64>::new();
+    for mut secret in INPUT {
+        let mut sequence: [i8; 4] = [0, 0, 0, 0];
+        let mut used = HashSet::<[i8; 4]>::new();
+        for i in 0..2000 {
+            let last_bananas: i8 = (secret % 10).try_into().unwrap();
+            secret ^= secret * 64;
+            secret %= 16777216;
+            secret ^= secret / 32;
+            secret %= 16777216;
+            secret ^= secret * 2048;
+            secret %= 16777216;
+            sequence[0] = sequence[1];
+            sequence[1] = sequence[2];
+            sequence[2] = sequence[3];
+            sequence[3] = TryInto::<i8>::try_into(secret % 10).unwrap() - last_bananas;
+
+            if i < 4 || used.contains(&sequence) { continue } // Skip first 4 numbers, they can never form a real sequence
+            *sequences.entry(sequence).or_default() += secret % 10;
+            used.insert(sequence);
+        }
+    }
+
+    println!("Result: {}", sequences.values().max().unwrap());
+}