From f965a52d4034fd5c159dceb6567fbb79932957d2 Mon Sep 17 00:00:00 2001
From: Justin Worthe <justin@worthe-it.co.za>
Date: Sat, 8 Dec 2018 07:30:24 +0200
Subject: Day 8: Recursing the tree

---
 src/bin/day_8.rs | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 51 insertions(+), 3 deletions(-)

(limited to 'src/bin/day_8.rs')

diff --git a/src/bin/day_8.rs b/src/bin/day_8.rs
index ff1db8a..59813b0 100644
--- a/src/bin/day_8.rs
+++ b/src/bin/day_8.rs
@@ -4,15 +4,63 @@ 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 = read_file(&PathBuf::from("inputs/8.txt"))?;
-
-    println!("Input: {:?}", input);
+    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()
+    }
+}
-- 
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