Day 13, puzzle 2

src/bin/d13p2.rs

@@ -0,0 +1,24 @@
+use aoc22::{
+    day13::{self, Node},
+    util,
+};
+use itertools::Itertools;
+
+pub fn main() {
+    let mut pairs = day13::parse_pairs(&util::parse_input());
+    let mut packets = Vec::new();
+    while let Some(pair) = pairs.pop() {
+        packets.push(pair.0);
+        packets.push(pair.1);
+    }
+    let div1 = Node::List(vec![Node::List(vec![Node::Num(2)])]);
+    let div2 = Node::List(vec![Node::List(vec![Node::Num(6)])]);
+    packets.push(div1.clone());
+    packets.push(div2.clone());
+
+    packets.sort();
+    let n1 = packets.iter().find_position(|p| **p == div1).unwrap().0 + 1;
+    let n2 = packets.iter().find_position(|p| **p == div2).unwrap().0 + 1;
+
+    println!("Decoder key: {}", n1 * n2);
+}

src/day13.rs

@@ -2,52 +2,56 @@ use std::cmp::Ordering;
 
 use itertools::{EitherOrBoth, Itertools};
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum Node {
     List(Vec<Node>),
     Num(usize),
 }
 
-impl PartialOrd for Node {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+impl Ord for Node {
+    fn cmp(&self, other: &Self) -> Ordering {
         match self {
             Node::List(l1) => match other {
-                Node::Num(n2) => self.partial_cmp(&Node::List(vec![Node::Num(*n2)])),
+                Node::Num(n2) => self.cmp(&Node::List(vec![Node::Num(*n2)])),
                 Node::List(l2) => {
                     for pair in l1.iter().zip_longest(l2.iter()) {
                         match pair {
                             EitherOrBoth::Both(n1, n2) => {
                                 if n1 < n2 {
-                                    return Some(Ordering::Less);
+                                    return Ordering::Less;
                                 } else if n2 < n1 {
-                                    return Some(Ordering::Greater);
+                                    return Ordering::Greater;
                                 }
                             }
-                            EitherOrBoth::Left(_) => return Some(Ordering::Greater),
-                            EitherOrBoth::Right(_) => return Some(Ordering::Less),
+                            EitherOrBoth::Left(_) => return Ordering::Greater,
+                            EitherOrBoth::Right(_) => return Ordering::Less,
                         }
                     }
-                    Some(Ordering::Equal)
+                    Ordering::Equal
                 }
             },
             Node::Num(n1) => match other {
-                Node::Num(n2) => n1.partial_cmp(n2),
-                Node::List(_) => Node::List(vec![Node::Num(*n1)]).partial_cmp(other),
+                Node::Num(n2) => n1.cmp(n2),
+                Node::List(_) => Node::List(vec![Node::Num(*n1)]).cmp(other),
             },
         }
     }
 }
 
+impl PartialOrd for Node {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
 impl PartialEq for Node {
     fn eq(&self, other: &Self) -> bool {
         self.partial_cmp(other) == Some(Ordering::Equal)
     }
-
-    fn ne(&self, other: &Self) -> bool {
-        !self.eq(other)
-    }
 }
 
+impl Eq for Node {}
+
 pub fn parse_pairs(input: &String) -> Vec<(Node, Node)> {
     let mut result = Vec::new();