1 files changed, 62 insertions, 0 deletions
diff --git a/2017/src/bin/day_7.rs b/2017/src/bin/day_7.rs
new file mode 100644
index 0000000..3c3b185
--- /dev/null
+++ b/2017/src/bin/day_7.rs
@@ -0,0 +1,62 @@
+extern crate advent_of_code_2017;
+use advent_of_code_2017::*;
+
+extern crate regex;
+use regex::Regex;
+
+fn main() {
+    let args = AdventArgs::init();
+
+    let names_re = Regex::new(r"[a-z]+").unwrap();
+    let weight_re = Regex::new(r"\d+").unwrap();
+
+    let tree: Vec<(String, Vec<String>, i32)> = args.input.iter()
+        .map(|line| {
+            let mut matches = names_re.find_iter(line);
+            let base = matches.next().unwrap().as_str().to_string();
+            let leaves = matches.map(|m| m.as_str().to_string()).collect();
+            let weight = weight_re.find(line).unwrap().as_str().parse().unwrap();
+            (base, leaves, weight)
+        }).collect();
+
+    let mut possible_roots: Vec<String> = tree.iter().map(|&(ref id, _, _)| id.clone()).collect();
+    for &(_, ref leaves, _) in &tree {
+        for leaf in leaves  {
+            let index = possible_roots.iter().position(|x| x == leaf).unwrap();
+            possible_roots.remove(index);
+        }
+    }
+    let root = &possible_roots[0];
+    
+    if args.part == 1 {
+        println!("{:?}", root);
+    } else {
+        find_unweighted_plate(&root, &tree);
+    }
+}
+
+fn find_unweighted_plate(root: &String, tree: &Vec<(String, Vec<String>, i32)>) -> i32 {
+    let root_node = find_node(&root, &tree);
+    let &(_, ref leaves, ref weight) = root_node;
+    let leaf_weights: Vec<i32> = leaves.iter().map(|leaf| {
+        find_unweighted_plate(&leaf, &tree)
+    }).collect();
+
+    if let Some(base_leaf_weight) = leaf_weights.first() {
+        if let Some(different_leaf_weight) = leaf_weights.iter().find(|&w| w != base_leaf_weight) {
+            println!("Unbalanced plate is off by {}", (different_leaf_weight-base_leaf_weight).abs());
+            println!("Towers on plate: {:?} weigh {:?}", leaves, leaf_weights);
+            // This still needs some manual work to get to the puzzle
+            // output. Take the first unbalanced plate, figure out
+            // which is the unbalanced tower visually, find its
+            // individual weight in the file, and add/subtract as
+            // necessary.
+        }
+    }
+
+    leaf_weights.iter().sum::<i32>() + weight
+}
+
+fn find_node<'a>(name: &String, tree: &'a Vec<(String, Vec<String>, i32)>) -> &'a (String, Vec<String>, i32) {
+    tree.iter().find(|&&(ref id, _, _)| id == name).unwrap()
+}