1 files changed, 115 insertions, 0 deletions

diff --git a/day8/src/main.rs b/day8/src/main.rs
new file mode 100644
index 0000000..4d18938
--- /dev/null
+++ b/day8/src/main.rs
@@ -0,0 +1,115 @@
+use std::env;
+use std::io::BufReader;
+use std::io::BufRead;
+use std::fs::File;
+use std::process;
+
+struct Node {
+  n_children: usize,
+  n_metadata: usize,
+  children: Vec<Node>,
+  metadata: Vec<u32>
+}
+
+impl Node {
+  fn value(&self) -> u32 {
+    if self.n_children == 0 {
+      sum_metadata(&self)
+    } else {
+      let mut value: u32 = 0;
+      for metadatum in &self.metadata {
+        let i = (metadatum - 1) as usize;
+        if i >= self.n_children {
+          continue;
+        }
+        let child = &self.children[i];
+        value += child.value();
+      }
+      value
+    }
+  }
+}
+
+fn build_tree(nums: &Vec<u32>, offset: usize, depth: u32) -> (Node, usize) {
+  let mut i: usize = offset;
+  for _k in 0..depth {
+    print!("    ");
+  }
+
+  let n_children = nums[i] as usize;
+  i += 1;
+
+  let n_metadata = nums[i] as usize;
+  i += 1;
+
+  println!("n_children: {}, n_metadata: {}", n_children, n_metadata);
+  let mut children: Vec<Node> = Vec::new();
+  let mut metadata: Vec<u32> = Vec::new();
+  for _j in 0..n_children {
+    let (child, size) = build_tree(&nums, i, depth + 1);
+    i += size;
+    children.push(child);
+  }
+  for j in 0..n_metadata {
+    let metadatum = nums[i];
+    i += 1;
+    metadata.push(metadatum);
+  }
+
+  let node = Node { n_children, n_metadata, children, metadata };
+  (node, i - offset)
+}
+
+fn sum_metadata(node: &Node) -> u32 {
+  let mut result: u32 = 0;
+  for metadatum in &node.metadata {
+    result += metadatum;
+  }
+
+  for child in &node.children {
+    let sum = sum_metadata(child);
+    result += sum;
+  }
+
+  result
+}
+
+fn main() {
+  let args: Vec<String> = env::args().collect();
+  if args.len() != 2 {
+    println!("Wrong number of arguments. Provide a file name and worker count.");
+    process::exit(1);
+  }
+  let filename = &args[1];
+
+  println!("Using file {} as input.", filename);
+  let f = match File::open(filename) {
+    Ok(file) => file,
+    Err(e) => {
+      println!("Failed to open file {}. {:?}", filename, e);
+      process::exit(1);
+    }
+  };
+  let file = BufReader::new(&f);
+  let lines: Vec<String> = file.lines()
+    .map(|line| line.expect("Could not parse line."))
+    .collect();
+
+  let is_more_than_one_line = lines.len() >= 1;
+  assert!(is_more_than_one_line);
+
+  let line_chars = &lines[0];
+  let strs: Vec<&str> = line_chars.split(" ").collect();
+  let mut nums: Vec<u32> = Vec::new();
+  for s in &strs {
+    let num: u32 = s.parse().expect("Could not convert value to u32");
+    nums.push(num);
+  }
+
+  let (tree, _size) = build_tree(&nums, 0, 0);
+  let result_1 = sum_metadata(&tree);
+  println!("1. Result: {}", result_1);
+
+  let result_2 = tree.value();
+  println!("2. Result: {}", result_2);
+}
\ No newline at end of file