Merge branch '2018-main'

1 files changed, 66 insertions, 0 deletions

diff --git a/2018/src/bin/day_8.rs b/2018/src/bin/day_8.rs
new file mode 100644
index 0000000..59813b0
--- /dev/null
+++ b/2018/src/bin/day_8.rs
@@ -0,0 +1,66 @@
+extern crate advent_of_code_2018;
+use advent_of_code_2018::*;
+
+use std::error::Error;
+use std::path::PathBuf;
+
+use std::slice::Iter;
+
+// cargo watch -cs "cargo run --release --bin day_8"
+
+fn main() -> Result<(), Box<Error>> {
+    let input: Vec<u32> = read_file(&PathBuf::from("inputs/8.txt"))
+        .map(|lines| lines[0]
+             .split_whitespace()
+             .map(|s| s.parse().unwrap())
+             .collect()
+        )?;
+
+    //println!("Input: {:?}", input);
+
+    let metadata_sum = sum_metadata(&mut input.iter());
+    debug!(metadata_sum);
+
+    let value = node_value(&mut input.iter());
+    debug!(value);
+
+    Ok(())
+}
+
+fn sum_metadata(iter: &mut Iter<'_, u32>) -> u32 {
+    let num_children = iter.next().unwrap().clone();
+    let num_metadata = iter.next().unwrap().clone();
+
+    let children_sum: u32 = (0..num_children)
+        .map(|_| sum_metadata(iter))
+        .sum();
+
+    let metadata_sum: u32 = (0..num_metadata)
+        .map(|_| iter.next().unwrap())
+        .sum();
+
+    children_sum + metadata_sum
+}
+
+
+fn node_value(iter: &mut Iter<'_, u32>) -> u32 {
+    let num_children = iter.next().unwrap().clone();
+    let num_metadata = iter.next().unwrap().clone();
+
+    let node_values: Vec<u32> = (0..num_children)
+        .map(|_| node_value(iter))
+        .collect();
+
+    let metadata: Vec<u32> = (0..num_metadata)
+        .map(|_| iter.next().unwrap().clone())
+        .collect();
+
+    if num_children == 0 {
+        metadata.iter().sum()
+    } else {
+        metadata.iter()
+            .filter(|m| **m > 0 && **m-1 < num_children)
+            .map(|m| node_values[*m as usize - 1])
+            .sum()
+    }
+}