Day 22 solutions

Author: Cadiac

README.md

@@ -107,3 +107,4 @@ This should start the server at `localhost:8080`.
 ❄️ [Day 19](aoc-solver/src/y2024/day19.rs)
 ❄️ [Day 20](aoc-solver/src/y2024/day20.rs)
 ❄️ [Day 21](aoc-solver/src/y2024/day21.rs)
+❄️ [Day 22](aoc-solver/src/y2024/day22.rs)

aoc-solver/src/y2024/day22.rs

@@ -0,0 +1,137 @@
+use std::collections::HashMap;
+
+use itertools::Itertools;
+
+use crate::solution::{AocError, Solution};
+
+fn parse(input: &str) -> Result<Vec<u64>, AocError> {
+    input
+        .lines()
+        .map(|row| row.parse::<u64>().map_err(|err| AocError::parse(row, err)))
+        .try_collect()
+}
+
+fn evolve(mut secret: u64) -> u64 {
+    // Calculate the result of multiplying the secret number by 64.
+    // Then, mix this result into the secret number.
+    // Finally, prune the secret number.
+    secret ^= secret * 64;
+    secret %= 16777216;
+
+    // Calculate the result of dividing the secret number by 32.
+    // Then, mix this result into the secret number.
+    // Finally, prune the secret number.
+    secret ^= secret / 32;
+    secret %= 16777216;
+
+    // Calculate the result of multiplying the secret number by 2048.
+    // Then, mix this result into the secret number.
+    // Finally, prune the secret number.
+    secret ^= secret * 2048;
+    secret %= 16777216;
+
+    secret
+}
+
+pub struct Day22;
+impl Solution for Day22 {
+    type A = u64;
+    type B = u64;
+
+    fn default_input(&self) -> &'static str {
+        include_str!("../../../inputs/2024/day22.txt")
+    }
+
+    fn part_1(&self, input: &str) -> Result<u64, AocError> {
+        let secrets = parse(input)?;
+
+        let sum = secrets
+            .into_iter()
+            .map(|initial_secret| (0..2000).fold(initial_secret, |secret, _| evolve(secret)))
+            .sum();
+
+        Ok(sum)
+    }
+
+    fn part_2(&self, input: &str) -> Result<u64, AocError> {
+        let secrets = parse(input)?;
+
+        let every_buyer_sequences = secrets
+            .into_iter()
+            .map(|mut secret| {
+                let mut prices = Vec::new();
+                let mut diffs = Vec::new();
+
+                for _ in 1..2000 {
+                    let prev_price = secret % 10;
+                    secret = evolve(secret);
+                    let price = secret % 10;
+
+                    prices.push(price);
+                    diffs.push(price as i64 - prev_price as i64);
+                }
+
+                let price_by_sequence = diffs.windows(4).enumerate().fold(
+                    HashMap::new(),
+                    |mut sequences, (i, window)| {
+                        sequences.entry(window.to_vec()).or_insert(prices[i + 3]);
+                        sequences
+                    },
+                );
+
+                price_by_sequence
+            })
+            .collect::<Vec<_>>();
+
+        let mut bananas_by_sequence: HashMap<Vec<i64>, u64> = HashMap::new();
+
+        for sequences in every_buyer_sequences {
+            for (sequence, price) in sequences.into_iter() {
+                *bananas_by_sequence.entry(sequence).or_insert(0) += price;
+            }
+        }
+
+        let most_bananas = bananas_by_sequence
+            .into_values()
+            .max()
+            .ok_or_else(|| AocError::logic("No bananas?"))?;
+
+        Ok(most_bananas)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_solves_part1_example() {
+        assert_eq!(
+            Day22.part_1(
+                "1\n\
+                 10\n\
+                 100\n\
+                 2024"
+            ),
+            Ok(37327623)
+        );
+    }
+
+    #[test]
+    fn it_solves_part2_example() {
+        assert_eq!(
+            Day22.part_2(
+                "1\n\
+                 2\n\
+                 3\n\
+                 2024"
+            ),
+            Ok(23)
+        );
+    }
+
+    #[test]
+    fn it_evolves_correctly() {
+        assert_eq!(evolve(123), 15887950);
+    }
+}

aoc-solver/src/y2024/mod.rs

@@ -21,12 +21,12 @@ pub mod day18;
 pub mod day19;
 pub mod day20;
 pub mod day21;
-// pub mod day22;
+pub mod day22;
 // pub mod day23;
 // pub mod day24;
 // pub mod day25;
 
-pub const MAX_DAYS: u8 = 21;
+pub const MAX_DAYS: u8 = 22;
 
 pub struct Y2024;
 
@@ -54,7 +54,7 @@ impl Solver for Y2024 {
             19 => day19::Day19.run(input, 19, 2024),
             20 => day20::Day20.run(input, 20, 2024),
             21 => day21::Day21.run(input, 21, 2024),
-            // 22 => day22::Day22.run(input, 22, 2024),
+            22 => day22::Day22.run(input, 22, 2024),
             // 23 => day23::Day23.run(input, 23, 2024),
             // 24 => day24::Day24.run(input, 24, 2024),
             // 25 => day25::Day25.run(input, 25, 2024),
@@ -96,7 +96,7 @@ impl Solver for Y2024 {
             19 => include_str!("./day19.rs"),
             20 => include_str!("./day20.rs"),
             21 => include_str!("./day21.rs"),
-            // 22 => include_str!("./day22.rs"),
+            22 => include_str!("./day22.rs"),
             // 23 => include_str!("./day23.rs"),
             // 24 => include_str!("./day24.rs"),
             // 25 => include_str!("./day25.rs"),

aoc-web/src/header.rs

@@ -42,6 +42,7 @@ pub fn header(props: &HeaderProps) -> Html {
                                     <NavLink route={Route::Solution { year: 2024, day: 19 }} current={props.route.clone()} text={"19"}/>
                                     <NavLink route={Route::Solution { year: 2024, day: 20 }} current={props.route.clone()} text={"20"}/>
                                     <NavLink route={Route::Solution { year: 2024, day: 21 }} current={props.route.clone()} text={"21"}/>
+                                    <NavLink route={Route::Solution { year: 2024, day: 22 }} current={props.route.clone()} text={"22"}/>
                                 </>
                             }
                         },