From 1aa90ba9dbb42f03c6272b1a393e3fc9a9a98d9f Mon Sep 17 00:00:00 2001
From: sepia <soerxpso@gmail.com>
Date: Mon, 23 Dec 2024 00:55:21 -0600
Subject: [PATCH] Day 22 (catching up!)

---
 src/day22.rs | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.rs  |  4 +++-
 2 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 src/day22.rs

diff --git a/src/day22.rs b/src/day22.rs
new file mode 100644
index 0000000..9d90d1d
--- /dev/null
+++ b/src/day22.rs
@@ -0,0 +1,64 @@
+use std::collections::{HashMap, HashSet};
+
+type Sequence = (i8, i8, i8, i8);
+
+pub fn day22() {
+    let initial_numbers: Vec<u64> = crate::input(22)
+        .lines()
+        .map(|x| x.parse().unwrap())
+        .collect();
+
+    let mut total_sequence_values: HashMap<Sequence, u64> = HashMap::new();
+    for &vendor_secret in initial_numbers.iter() {
+        let price_data = price_data(vendor_secret);
+        let mut seen_sequences: HashSet<Sequence> = HashSet::new();
+        for window in price_data.windows(4) {
+            let sequence: Sequence = (window[0].1, window[1].1, window[2].1, window[3].1);
+            let price = window[3].0;
+            if !seen_sequences.contains(&sequence) {
+                *total_sequence_values.entry(sequence.clone()).or_insert(0) += price as u64;
+                seen_sequences.insert(sequence);
+            }
+        }
+    }
+
+    let (best_sequence, best_price) = total_sequence_values
+        .into_iter()
+        .max_by_key(|&(_, price)| price)
+        .unwrap();
+    println!("Best Sequence: {:?}, Price: {}", best_sequence, best_price);
+
+    let mut total: u64 = 0;
+    for mut number in initial_numbers {
+        for _ in 0..2000 {
+            number = evolve_secret_number(number);
+        }
+        total += number;
+    }
+    println!("Sum of Final Secret Numbers: {total}");
+}
+
+fn price_data(mut secret: u64) -> Vec<(u8, i8)> {
+    let mut prices = vec![last_digit(secret)];
+    for _ in 0..2000 {
+        secret = evolve_secret_number(secret);
+        prices.push(last_digit(secret));
+    }
+    let mut ret: Vec<(u8, i8)> = vec![];
+    for i in 1..prices.len() {
+        let change = prices[i] as i8 - prices[i - 1] as i8;
+        ret.push((prices[i], change));
+    }
+    ret
+}
+
+fn last_digit(number: u64) -> u8 {
+    (number % 10) as u8
+}
+
+fn evolve_secret_number(mut number: u64) -> u64 {
+    number = (number ^ (64 * number)) % 16777216;
+    number = (number ^ (number / 32)) % 16777216;
+    number = (number ^ (number * 2048)) % 16777216;
+    number
+}
diff --git a/src/main.rs b/src/main.rs
index 29d8a88..604b8e5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -26,7 +26,9 @@ mod day19;
 mod day2;
 #[allow(dead_code)]
 mod day20;
+#[allow(dead_code)]
 mod day21;
+mod day22;
 #[allow(dead_code)]
 mod day3;
 #[allow(dead_code)]
@@ -43,7 +45,7 @@ mod day8;
 mod day9;
 
 fn main() {
-    day21::day21();
+    day22::day22();
 }
 
 pub fn input(day: u8) -> String {