Day 20, part 2

src/bin/d20p1.rs

@@ -1,7 +1,7 @@
 use aoc22::{day20, util};
 
 pub fn main() {
-    let nodes = day20::parse_file(&util::parse_input());
+    let nodes = day20::parse_file(&util::parse_input(), 1);
 
     day20::mix(&nodes);
 

src/bin/d20p2.rs

@@ -0,0 +1,16 @@
+use aoc22::{day20, util};
+
+const KEY: isize = 811589153;
+const ROUNDS: usize = 10;
+
+pub fn main() {
+    let nodes = day20::parse_file(&util::parse_input(), KEY);
+    // day20::print_nodes(&nodes);
+
+    for _ in 0..ROUNDS {
+        day20::mix(&nodes);
+        // day20::print_nodes(&nodes);
+    }
+
+    println!("Sum of coordinates: {}", day20::calc_coordinates(&nodes));
+}

src/day20.rs

@@ -35,14 +35,14 @@ pub fn get_prev(node: &Rc<RefCell<Node>>, n: usize) -> Rc<RefCell<Node>> {
     curr
 }
 
-pub fn parse_file(input: &String) -> Vec<Rc<RefCell<Node>>> {
+pub fn parse_file(input: &String, key: isize) -> Vec<Rc<RefCell<Node>>> {
     let mut result = Vec::new();
 
     let mut last = None;
     for line in input.lines() {
         let val: isize = line.parse().unwrap();
         let node = Rc::new(RefCell::new(Node {
-            val,
+            val: val * key,
             next: None,
             prev: last.clone(),
         }));
@@ -64,9 +64,11 @@ pub fn parse_file(input: &String) -> Vec<Rc<RefCell<Node>>> {
 }
 
 pub fn mix(nodes: &Vec<Rc<RefCell<Node>>>) {
+    let div = nodes.len() - 1;
+
     for node in nodes {
         let n = node.borrow().val;
-        if n == 0 {
+        if n == 0 || (n > 0 && (n as usize) % div == 0) || (n < 0 && (-n as usize) % div == 0) {
             continue;
         }
 
@@ -77,9 +79,13 @@ pub fn mix(nodes: &Vec<Rc<RefCell<Node>>>) {
         next.borrow_mut().prev = Some(prev.clone());
 
         let prev = if n > 0 {
-            get_next(node, n as usize)
+            let n = (n as usize) % div;
+            assert!(n < div);
+            get_next(node, n)
         } else {
-            get_prev(node, (-n as usize) + 1)
+            let n = ((-n as usize) % div) + 1;
+            assert!(n < div);
+            get_prev(node, n)
         };
         let next = get_next(&prev, 1);
         prev.deref().borrow_mut().next = Some(node.clone());
@@ -89,8 +95,6 @@ pub fn mix(nodes: &Vec<Rc<RefCell<Node>>>) {
         n_mut.prev = Some(prev.clone());
         n_mut.next = Some(next.clone());
         drop(n_mut);
-
-        // print_nodes(&nodes);
     }
 }