work on exploding and splitting

2021/src/day18.rs

@@ -11,12 +11,27 @@ enum Item {
     SubPair(Box<Pair>),
 }
 
+impl Item {
+    fn magnitude(&self) -> usize {
+        match self {
+            Item::Value(v) => *v as usize,
+            Item::SubPair(pair) => pair.magnitude(),
+        }
+    }
+}
+
 #[derive(Debug)]
 struct Pair {
     left: Item,
     right: Item,
 }
 
+impl Pair {
+    fn magnitude(&self) -> usize {
+        3 * self.left.magnitude() + 2 * self.right.magnitude()
+    }
+}
+
 
 struct Parser<'a> {
     chars: Chars<'a>,
@@ -25,7 +40,7 @@ struct Parser<'a> {
 impl<'a> Parser<'a> {
     fn from(src: &'a str) -> Parser<'a> {
         let mut chars = src.chars();
-        chars.next(); // throw away the opening bracket
+        chars.next(); // throw away the opening bracket so we don't nest too deeply
         Parser {chars}
     }
 
@@ -52,21 +67,24 @@ fn load(data: &str) -> eyre::Result<Vec<Pair>>{
     let mut pairs = Vec::new();
     for line in data.lines() {
         let mut parser = Parser::from(line);
-        match parser.parse() {
-            Ok(pair) => pairs.push(pair),
-            Err(e) => return Err(eyre!("Invalid input: {}", line)),
-        }
+        let pair = parser.parse()
+            .map_err(|_| eyre!("Invalid input: {}", line))?;
+        pairs.push(pair);
     }
     Ok(pairs)
 }
 
 
-const _SAMPLE: &str = "[[1,9],[8,5]]";
+const _SAMPLE: &str = "[[[[8,7],[7,7]],[[8,6],[7,7]]],[[[0,7],[6,6]],[8,7]]]";
 
 pub fn run(data: &str) -> eyre::Result<(usize, usize)> {
-    let pairs = load(data)?;
-    dbg!(pairs.len());
-    dbg!(&pairs[0]);
+    // let pairs = load(data)?;
+    // dbg!(pairs.len());
+    // dbg!(&pairs[0]);
+
+    let mut parser = Parser::from(_SAMPLE);
+    let root = parser.parse()?;
+    dbg!(root.magnitude());
 
     Ok((0, 0))
 }