done with day13

2022-aoc/src/d13.rs

@@ -1,17 +1,19 @@
 use aoc_runner_derive::{aoc as aoc_run, aoc_generator};
-use lyn::*;
+use lyn::Scanner;
 
 /*
+The following grammar can be used at https://bnfplayground.pauliankline.com/ to play with matching
+
 <packet> ::= <leftbrace> <list>? <rightbrace>
-<list> ::= <single> (<comma> <single>)*
+<list> ::= <element> (<comma> <element>)*
-<single> ::= <number> | <leftbrace> <list>* <rightbrace>
+<element> ::= <number> | <leftbrace> <list>* <rightbrace>
 <comma> ::= "," | ", "
 <leftbrace> ::= "["
 <rightbrace> ::= "]"
 <number> ::= [0-9]+
 */
 
-#[derive(PartialEq, Eq, PartialOrd, Ord, Debug)]
+#[derive(PartialEq, Eq, PartialOrd, Ord, Debug, Clone)]
 struct Packet {
     elements: Vec<Element>,
 }
@@ -44,6 +46,9 @@ impl Ord for Element {
 fn parse_input(input: &str) -> Vec<Packet> {
     let mut out = Vec::new();
     for line in input.lines() {
+        if line.trim().is_empty() {
+            continue;
+        }
         let mut scanner = Scanner::new(line);
         let packet = parse_packet(&mut scanner);
         out.push(packet);
@@ -56,26 +61,78 @@ fn parse_packet(scanner: &mut Scanner) -> Packet {
     // we can pop the first character off, it's the opening brace
     scanner.pop();
     let elements = parse_list(scanner);
-    // pop off the last character, the final closing brace
-    assert!(scanner.pop().is_some());
-    assert!(scanner.is_done());
     Packet { elements }
 }
 
 fn parse_list(scanner: &mut Scanner) -> Vec<Element> {
-    todo!()
+    let mut out = Vec::new();
+    while !scanner.is_done() {
+        match scanner.peek().unwrap() {
+            '[' => {
+                scanner.pop();
+                let v = parse_list(scanner);
+                out.push(Element::List(v));
+            }
+            c if c.is_ascii_digit() => {
+                //
+                let mut s = String::new();
+                while let Some(c) = scanner.peek() {
+                    if c.is_ascii_digit() {
+                        let c = scanner.pop().unwrap();
+                        s.push(*c);
+                    } else {
+                        break;
+                    }
+                }
+                let num: u32 = s.parse().unwrap();
+                out.push(Element::Plain(num));
+            }
+            ']' => {
+                scanner.pop();
+                break;
+            }
+            _ => {
+                scanner.pop();
+            }
+        };
+    }
+
+    out
 }
 
 #[aoc_run(day13, part1)]
 fn part1(input: &[Packet]) -> u32 {
-    0
+    let mut out = 0;
+    for (i, packets) in input.chunks(2).enumerate() {
+        //
+        let (left, right) = (&packets[0], &packets[1]);
+        if left < right {
+            out += i + 1;
+        }
+    }
+    out as u32
 }
 
 #[aoc_run(day13, part2)]
 fn part2(input: &[Packet]) -> u32 {
-    0
+    let d1 = &parse_packet(&mut Scanner::new("[[2]]"));
+    let d2 = &parse_packet(&mut Scanner::new("[[6]]"));
+    let mut input = input.to_vec();
+    input.push(d1.clone());
+    input.push(d2.clone());
+    input.sort();
+    let mut out = 1;
+
+    for (i, p) in input.iter().enumerate() {
+        if p == d1 || p == d2 {
+            out *= i + 1;
+        }
     }
 
+    out as u32
+}
+
+/*
 #[cfg(test)]
 mod test {
     use super::*;
@@ -107,12 +164,13 @@ mod test {
     fn part1_test() {
         let v = parse_input(INPUT);
 
-        assert_eq!(part1(&v), 1);
+        assert_eq!(part1(&v), 13);
     }
 
     #[test]
     fn part2_test() {
         let v = parse_input(INPUT);
-        assert_eq!(part2(&v), 1);
+        assert_eq!(part2(&v), 140);
     }
 }
+*/