day13

2 files changed, 117 insertions, 0 deletions

diff --git a/src/day13.rs b/src/day13.rs
new file mode 100644
index 0000000..d2bd050
--- /dev/null
+++ b/src/day13.rs
@@ -0,0 +1,115 @@
+use std::cmp::Ordering;
+
+#[derive(Debug,Clone,PartialEq)]
+enum Packet {
+    Num(i32),
+    Lst(Vec<Packet>)
+}
+
+impl Packet {
+    fn parse<T: Iterator<Item = char>>(chrs: &mut T) -> Packet {
+        let mut numchrs = String::new();
+        let mut children: Vec<Packet> = Vec::new();
+        loop {
+            match chrs.next() {
+                Some('[') => {
+                    children.push(Packet::parse(chrs));
+                },
+                Some(']') | None => break,
+                Some(',') => {
+                    if !numchrs.is_empty() {
+                        children.push(Packet::Num(numchrs.parse().expect("chars wasn't a number!")));
+                    }
+                    numchrs.clear();
+                }, 
+                Some(x) => {
+                    numchrs.push(x);
+                },
+            }
+        }
+        if !numchrs.is_empty() {
+            children.push(Packet::Num(numchrs.parse().expect("chars wasn't a number!")));
+        }
+        Packet::Lst(children)
+    }
+    fn coerce_to_lst(&self) -> Packet {
+        match self {
+            Self::Lst(x) => Packet::Lst(x.to_vec()),
+            Self::Num(x) => Packet::Lst(vec![Packet::Num(*x)])
+        }
+    }
+    fn rightorder(left: &Packet, right: &Self) -> Ordering {
+        if let (Packet::Num(x), Packet::Num(y)) = (left, right) {
+            if x < y {
+                Ordering::Less
+            } else if x == y {
+                Ordering::Equal
+            } else {
+                Ordering::Greater
+            }
+        } else if let (Packet::Lst(x), Packet::Lst(y)) = (left, right) {
+            for ix in 0..(x.len().max(y.len())) {
+                let maybe_xx = x.get(ix);
+                if maybe_xx.is_none() {
+                    return Ordering::Less;
+                }
+                let maybe_yy = y.get(ix);
+                if maybe_yy.is_none() {
+                    return Ordering::Greater;
+                }
+                let rr = Packet::rightorder(maybe_xx.unwrap(), maybe_yy.unwrap());
+                match rr {
+                    Ordering::Less | Ordering::Greater => return rr,
+                    Ordering::Equal => {},
+                }
+            }
+            Ordering::Equal
+        } else {
+            Packet::rightorder(&left.coerce_to_lst(), &right.coerce_to_lst())
+        }
+    }
+}
+
+pub fn run(input: String) {
+    // let x: i32 = input.lines().collect::<Vec<&str>>().split(|x| {x.is_empty()})
+    //     .enumerate()
+    //     .map(|(ix, ps)| {
+    //         if ps.len() != 2 {
+    //             panic!("Expected pairs of packets, got {:?}", ps);
+    //         }
+    //         let ps1 = ps[0];
+    //         let ps2 = ps[1];
+    //         let p1 = Packet::parse(&mut ps1.chars().into_iter());
+    //         let p2 = Packet::parse(&mut ps2.chars().into_iter());
+    //         //println!("ps1 {} ps2 {} p1 {:?} p2 {:?}", ps1, ps2, p1, p2);
+    //         match Packet::rightorder(&p1, &p2) {
+    //             Ordering::Less => (ix+1) as i32,
+    //             Ordering::Greater => 0 as i32,
+    //             Ordering::Equal => panic!("2 identical packets????")
+    //         }
+    //     })
+    //     .sum();
+
+    // println!("Day 13: {}", x);
+    let mut zinput = String::from("
+[[2]]
+[[6]]
+");
+    zinput.push_str(&input);
+    let mut packets = zinput.lines()
+        .filter(|x| {!x.is_empty()})
+        .map(|x| {Packet::parse(&mut x.chars().into_iter())})
+        .enumerate()
+        .collect::<Vec<(usize, Packet)>>();
+    packets.sort_by(|(_, p1), (_, p2)| { Packet::rightorder(p1, p2)});
+    let mut dp1: usize = 0;
+    let mut dp2: usize = 0;
+    for (nix, (oix, _)) in packets.into_iter().enumerate() {
+        if oix == 0 {
+            dp1 = nix+1;
+        } else if oix == 1 {
+            dp2 = nix+1;
+        }
+    }
+    println!("Day 13: {}", dp1*dp2);
+}
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 885a516..0b427f1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -14,6 +14,7 @@ mod day9;
 mod day10;
 mod day11;
 mod day12;
+mod day13;
 
 fn main() {
     day1::run(fs::read_to_string("input/day1.txt").expect("Failed to read input file!"));
@@ -28,4 +29,5 @@ fn main() {
     day10::run(fs::read_to_string("input/day10.txt").expect("Failed to read input file!"));
     day11::run(fs::read_to_string("input/day11.txt").expect("Failed to read input file!"));
     day12::run(fs::read_to_string("input/day12.txt").expect("Failed to read input file!"));
+    day13::run(fs::read_to_string("input/day13.txt").expect("Failed to read input file!"));
 }