day 22 part 2

src/day22.rs

@@ -1,4 +1,6 @@
-use std::{fs::read_to_string, ops::BitXor};
+use std::{collections::HashSet, fs::read_to_string, ops::BitXor};
+
+use itertools::Itertools;
 
 pub fn day_main() {
     let input = read_to_string("input/day22.txt").unwrap();
@@ -16,13 +18,17 @@ fn part1(input: &str) -> RiddleResult {
 fn solution(initial_secret: i64) -> i64 {
     let mut secret = initial_secret;
     for _ in 0..2000 {
-        secret = prune(mix(secret * 64, secret));
-        secret = prune(mix(secret / 32, secret));
-        secret = prune(mix(secret * 2048, secret))
+        secret = fun_name(secret);
     }
     secret
 }
 
+fn fun_name(secret: i64) -> i64 {
+    let secret = prune(mix(secret * 64, secret));
+    let secret = prune(mix(secret / 32, secret));
+    prune(mix(secret * 2048, secret))
+}
+
 fn mix(value: i64, secret: i64) -> i64 {
     value.bitxor(secret)
 }
@@ -31,15 +37,89 @@ fn prune(value: i64) -> i64 {
     value % 16777216
 }
 
-fn part2(_input: &str) -> RiddleResult {
-    0
+fn part2(input: &str) -> RiddleResult {
+    let deltas = input
+        .trim()
+        .lines()
+        .map(|is| is.parse().unwrap())
+        .map(|s| generate(s))
+        .collect_vec();
+
+    let all_quadruples = sequences(&deltas);
+    println!(
+        "we have {} different sequences to check",
+        all_quadruples.len()
+    );
+
+    all_quadruples
+        .into_iter()
+        .enumerate()
+        .map(|(n, seq)| {
+            if n % 100 == 0 {
+                println!("{n}");
+            }
+
+            deltas
+                .iter()
+                .map(|monkey| find_first(seq, monkey))
+                .flat_map(|first| first.map(|f| f.3.price).or(Some(0)))
+                .sum()
+        })
+        .max()
+        .unwrap()
+}
+
+fn sequences(deltas: &Vec<Vec<Foo>>) -> HashSet<(i64, i64, i64, i64)> {
+    let mut all_quadruples = HashSet::new();
+    for monkey in deltas {
+        monkey
+            .iter()
+            .skip(1)
+            .tuple_windows()
+            .for_each(|(a, b, c, d)| {
+                all_quadruples.insert((a.delta, b.delta, c.delta, d.delta));
+            });
+    }
+    all_quadruples
+}
+
+fn find_first(seq: (i64, i64, i64, i64), monkey: &Vec<Foo>) -> Option<(&Foo, &Foo, &Foo, &Foo)> {
+    monkey.iter().tuple_windows().find(|(a, b, c, d)| {
+        a.delta == seq.0 && b.delta == seq.1 && c.delta == seq.2 && d.delta == seq.3
+    })
+}
+
+fn generate(start: i64) -> Vec<Foo> {
+    let mut result = Vec::with_capacity(2000);
+    result.push(Foo {
+        secret: start,
+        price: start % 10,
+        delta: -999999,
+    });
+    for i in 1..=2000 {
+        let prev = result[i - 1].secret;
+        let next = fun_name(prev);
+        let price = next % 10;
+        let delta = price - result[i - 1].price;
+        result.push(Foo {
+            secret: next,
+            price,
+            delta,
+        });
+    }
+    result
+}
+
+#[derive(Debug, PartialEq, Eq)]
+struct Foo {
+    secret: i64,
+    price: i64,
+    delta: i64,
 }
 
 #[cfg(test)]
 mod test {
-    use super::{part1, part2};
-
-    const TEST_INPUT: &str = r"";
+    use super::*;
 
     #[test]
     fn test1() {
@@ -57,6 +137,25 @@ mod test {
 
     #[test]
     fn test2() {
-        assert_eq!(part2(TEST_INPUT), 0);
+        let input = "1
+2
+3
+2024
+        ";
+        assert_eq!(part2(input), 23);
+    }
+
+    #[test]
+    fn finds_first() {
+        let monkey = generate(123);
+        let f = find_first((-1, -1, 0, 2), &monkey);
+        assert_eq!(
+            &Foo {
+                secret: 12683156,
+                price: 6,
+                delta: 2,
+            },
+            f.unwrap().3
+        );
     }
 }

src/day24.rs

@@ -169,7 +169,7 @@ where
 
 #[cfg(test)]
 mod test {
-    use super::{part1, part2};
+    use super::part1;
 
     const TEST_INPUT: &str = r"x00: 1
 x01: 0
@@ -222,9 +222,4 @@ tnw OR pbm -> gnj";
     fn test1() {
         assert_eq!(part1(TEST_INPUT), 2024);
     }
-
-    #[test]
-    fn test2() {
-        assert_eq!(part2(TEST_INPUT), 0);
-    }
 }