100 lines
2.7 KiB
Rust
100 lines
2.7 KiB
Rust
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#![warn(clippy::all, clippy::pedantic)]
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mod common;
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use common::day_input;
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type ChildNode<T> = Box<BinaryTreeNode<T>>;
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#[derive(Debug, std::cmp::PartialEq)]
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struct BinaryTreeBranch<T> {
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left: ChildNode<T>,
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right: ChildNode<T>,
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}
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#[derive(Debug, std::cmp::PartialEq)]
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enum BinaryTreeNode<T> {
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Branch(BinaryTreeBranch<T>),
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Leaf(T),
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}
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fn crawl_for<T>(node: &BinaryTreeNode<T>, predicate: fn(&BinaryTreeNode<T>, u64) -> bool, current_depth: u64) -> Option<&BinaryTreeNode<T>> {
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if predicate(node, current_depth) {
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Some(node)
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} else if let BinaryTreeNode::Branch(branch) = node {
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if let Some(result) = crawl_for(&*branch.left, predicate, current_depth + 1) {
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Some(result)
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} else if let Some(result) = crawl_for(&*branch.right, predicate, current_depth + 1) {
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Some(result)
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} else {
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None
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}
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} else {
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None
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}
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}
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fn maybe_explode<T: std::fmt::Debug>(tree: &mut BinaryTreeNode<T>) -> bool {
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if let Some(node_to_explode) = crawl_for(tree, |node, d| {
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if let BinaryTreeNode::Branch(_) = node {
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// TODO: must both child nodes be leaves?
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d >= 3
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} else {
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false
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}
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}, 0) {
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// TODO: do explosion
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println!("{:#?}", node_to_explode);
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true
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} else {
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false
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}
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}
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fn parse_binary_tree(s: &str) -> Result<BinaryTreeNode<u64>, &'static str> {
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let chars = s.chars().peekable();
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let ch = chars.peek();
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if let Some(c) = ch {
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match c {
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'0'..='9' => Ok(BinaryTreeNode::Leaf(u64::from(*c) - ASCII_0))
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'[' => {
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it.next()
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parse_binary_tree(
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// TODO: parse left piece
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// TODO: parse right piece
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// do_parse_binary_tree(&s[1..], depth + 1)
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// TODO: parse end of this (']')
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}
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_ => Err("unknown char")
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}
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} else {
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Err("empty string")
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}
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}
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fn main() {
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let result = parse_binary_tree(&day_input(18));
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println!("Snailfish Homework: {:#?}", result);
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn parser() {
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assert_eq!(parse_binary_tree("y"), Err("unknown char"));
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assert_eq!(parse_binary_tree("9"), Ok(BinaryTreeNode::Leaf(9)));
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assert_eq!(parse_binary_tree("[[1,2],3]"), Ok(BinaryTreeNode::Branch(BinaryTreeBranch {
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left: Box::new(BinaryTreeNode::Branch(BinaryTreeBranch {
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left: Box::new(BinaryTreeNode::Leaf(1)),
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right: Box::new(BinaryTreeNode::Leaf(2)),
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})),
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right: Box::new(BinaryTreeNode::Leaf(3)),
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})));
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}
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#[test]
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fn needs_exploding() {
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}
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}
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