Day 16 part 2

src/main.rs

@@ -3,5 +3,5 @@ extern crate core;
 mod tasks;
 
 fn main() {
-    tasks::day23::run();
+    tasks::day16::run();
 }

src/tasks/day16.rs

@@ -1,16 +1,30 @@
-use itertools::Itertools;
-use num_integer::Integer;
+use std::collections::HashMap;
 use std::iter;
 
+use itertools::Itertools;
+
+const BASE_PATTERN: [i32; 4] = [0, 1, 0, -1];
 const INPUT: &str = "59750530221324194853012320069589312027523989854830232144164799228029162830477472078089790749906142587998642764059439173975199276254972017316624772614925079238407309384923979338502430726930592959991878698412537971672558832588540600963437409230550897544434635267172603132396722812334366528344715912756154006039512272491073906389218927420387151599044435060075148142946789007756800733869891008058075303490106699737554949348715600795187032293436328810969288892220127730287766004467730818489269295982526297430971411865028098708555709525646237713045259603175397623654950719275982134690893685598734136409536436003548128411943963263336042840301380655801969822";
 
 #[allow(dead_code)]
 pub fn run() {
     let input = to_digits(INPUT);
     task1(input.clone());
+    task2(to_digits("02935109699940807407585447034323"));
     task2(input.clone());
 }
 
+fn task1(input: Vec<V>) -> String {
+    let mut s = S { input, cache: HashMap::new() };
+    s.prep();
+    let result = format!("{:.*}", 8, (0..8).map(|position| {
+        let r = s.get(position, 100);
+        r
+    }).join(""));
+    println!("Task 1: {result}");
+    result
+}
+
 fn to_digits(input: &str) -> Vec<i32> {
     input
         .chars()
@@ -18,71 +32,88 @@ fn to_digits(input: &str) -> Vec<i32> {
         .collect_vec()
 }
 
-fn task1(input: Vec<i32>) -> String {
-    let p = [0, 1, 0, -1];
-    let result = (0..100).fold(input, |old, _| {
-        (1..=old.len())
-            .map(|position| {
-                let pattern = p
-                    .iter()
-                    .map(|x| std::iter::repeat(*x).take(position))
-                    .flatten();
-                let val: i32 = old
-                    .iter()
-                    .zip(std::iter::repeat(pattern).flatten().skip(1))
-                    .map(|(value, multiplier)| value * multiplier)
-                    .sum();
-                val.abs() % 10
-            })
-            .collect_vec()
-    });
-    let result = format!("{:.*}", 8, result.iter().join(""));
-    println!("Task 1: {result}");
+fn task2(input: Vec<i32>) -> String {
+    let big_input = iter::repeat(input.clone().into_iter())
+        .take(10_000)
+        .flatten()
+        .collect_vec();
+
+    let mut s = S { input: big_input, cache: HashMap::new() };
+    let result_position = format!("{}", input.split_at(7).0.iter().join("")).parse::<usize>().unwrap();
+    s.prep_after(result_position);
+    let result = format!("{:.*}", 8, (0..8).map(|position| {
+        let r = s.get(position + result_position, 100);
+        r
+    }).join(""));
+
+    println!("Task 2: {result}");
     result
 }
 
-fn task2(input: Vec<i32>) -> String {
-    let l = input.len() * 10_000;
-    let big_input = iter::repeat(input.clone().into_iter())
-        .flatten()
-        .take(l)
-        .collect_vec();
-    let p = [0, 1, 0, -1];
-    let result = (0..100).fold(big_input, |old, _| {
-        (1..=old.len())
-            .map(|position| {
-                let pattern = p.iter().map(|x| iter::repeat(*x).take(position)).flatten();
-                let iter = iter::repeat(pattern).flatten().skip(1);
-                let repeats_after = (4 * position).lcm(&input.len());
-                if repeats_after > l {
-                    l
-                } else {
-                    repeats_after
-                };
-                let part: i32 = iter::repeat(input.iter())
-                    .flatten()
-                    .zip(iter.clone())
-                    .take(repeats_after)
-                    .map(|(value, multiplier)| value * multiplier)
-                    .sum();
-                let part_fits = l / repeats_after;
-                let most_parts = part * part_fits as i32;
+type V = i32;
 
-                let number_rest = l / repeats_after;
-                let part_rest: i32 = iter
-                    .zip(iter::repeat(input.iter()).flatten())
-                    .take(number_rest)
-                    .map(|(value, multiplier)| value * multiplier)
-                    .sum();
+struct S {
+    input: Vec<V>,
+    cache: HashMap<(usize, usize), V>,
+}
 
-                (part_rest + most_parts) % 10
-            })
-            .collect_vec()
-    });
-    let offset = input[0..7].iter().join("").parse::<usize>().unwrap();
-    let message = result[offset..offset + 8].iter().join("");
-    println!("Task 2: {}", message);
-    message
+impl S {
+    fn pattern(&self, position: usize, size: usize) -> Vec<i32> {
+        let pattern = BASE_PATTERN.iter().map(|x| iter::repeat(*x).take(position)).flatten();
+        let iter = iter::repeat(pattern).flatten().skip(1).take(size);
+        iter.collect()
+    }
+
+    fn get(&mut self, index: usize, phase: usize) -> V {
+        if phase == 0 {
+            return self.input[index];
+        }
+
+        if self.cache.contains_key(&(phase, index)) {
+            return self.cache[&(phase, index)];
+        }
+
+        if index == self.input.len() - 1 {
+            let v = self.get(index, phase - 1);
+            self.cache.insert((phase, index), v);
+            return v;
+        }
+
+        if index > (self.input.len() / 2 + 1) {
+            let v = self.get(index + 1, phase) + self.get(index, phase - 1);
+            let v = v.abs() % 10;
+            self.cache.insert((phase, index), v);
+            return v;
+        }
+
+        let pattern = self.pattern(index + 1, self.input.len());
+        let val: i32 = pattern
+            .iter()
+            .enumerate()
+            .map(|(i, p)| if *p == 0 { 0 } else { *p * self.get(i, phase - 1) })
+            .sum();
+        let result = val.abs() % 10;
+        self.cache.insert((phase, index), result);
+        result
+    }
+
+    fn prep(&mut self) {
+        for phase in 1..=100 {
+            for i in 1..self.input.len() / 2 {
+                self.get(self.input.len() - i, phase);
+            }
+        }
+        println!("preparation done")
+    }
+
+    fn prep_after(&mut self, start: usize) {
+        for phase in 1..=100 {
+            for i in (start..self.input.len()).rev() {
+                self.get(i, phase);
+            }
+        }
+        println!("preparation done")
+    }
 }
 
 #[cfg(test)]
@@ -104,13 +135,30 @@ mod test {
             "52432133"
         );
     }
+
     #[test]
     fn test_part_1_solution() {
         assert_eq!(task1(to_digits(INPUT)), "84487724");
     }
 
     #[test]
-    fn test_part_2() {
+    fn test_part_2_solution() {
+        assert_eq!(task2(to_digits(INPUT)), "84692524");
+    }
+
+    #[test]
+    fn test_trivial() {
+        let mut s = S { input: to_digits("12345678"), cache: HashMap::new() };
+        s.prep();
+        let result = format!("{:.*}", 8, (0..8).map(|position| {
+            let r = s.get(position, 1);
+            r
+        }).join(""));
+        assert_eq!(result, "48226158");
+    }
+
+    #[test]
+    fn test_part_2_examples() {
         assert_eq!(
             task2(to_digits("02935109699940807407585447034323")),
             "78725270"

src/tasks/day23.rs

@@ -2,6 +2,7 @@ use std::collections::VecDeque;
 
 use crate::tasks::day05::{IntCodeComputer, load_ram, RAM};
 
+#[allow(dead_code)]
 pub fn run() {
     let ram = load_ram("input/day23.txt");
     part1(ram.clone());

src/tasks/day25.rs

@@ -0,0 +1,44 @@
+use std::io;
+
+use crate::tasks::day05::{IntCodeComputer, load_ram};
+
+#[allow(dead_code)]
+pub fn run() {
+    let ram = load_ram("input/day25.txt");
+    let mut computer = IntCodeComputer::new(vec![], ram);
+
+    loop {
+        let done = computer.run_until_input_empty();
+        println!("{}", to_ascii(computer.get_output()));
+        computer.clear_output();
+
+        if done {
+            println!("Game Over");
+            return;
+        }
+
+        let input = read_line();
+        computer.set_input(&input);
+    }
+
+    // needed items:
+    // fixed point
+    // polygon
+    // candy cane
+    // shell
+
+    // result: 136839232
+}
+
+fn to_ascii(output: &[i128]) -> String {
+    output.iter().map(|i| (*i as u8) as char).collect()
+}
+
+fn read_line() -> Vec<i128> {
+    let mut buffer = String::new();
+    io::stdin().read_line(&mut buffer).unwrap();
+    if !buffer.is_ascii() {
+        panic!("'{}' is not ascii input", buffer);
+    }
+    buffer.chars().map(|c| c as i128).collect()
+}

src/tasks/mod.rs

@@ -22,3 +22,4 @@ pub mod day21;
 pub mod day22;
 pub mod day23;
 pub mod day24;
+pub mod day25;