AoC day 7 part 2 solution

AoC7Solution.java

import java.io.File;
-snip-

public class AoC7Solution {

	static List<Node> nodes = new ArrayList<>();
	
	public static void main(String[] args) {
		// Read input
		try {
			Scanner input = new Scanner(new File("day7challengeinput"));
			while(input.hasNextLine()) {
				String line = input.nextLine();
				String name = line.split(" ")[0];
				int weight = Integer.parseInt(line.split(" ")[1].split("\\(")[1].split("\\)")[0]);
				Node n = new Node(name, weight);
				if(line.contains(" -> ")) {
					n.childrenStrings.addAll(Arrays.asList(line.split(" -> ")[1].split(", ")));
				}
				nodes.add(n);
			}
			input.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		// Hardcode determinism for the root node
		Node rootNode = null;
		for(Node n : nodes) {
			if(n.name.equals("svugo")) rootNode = n;
		}
		
		nodes.remove(rootNode);
		System.out.println(rootNode.name + " " + rootNode.weight);
		
		// assemble the tree from the trunk upwards, recursively
		assemble(rootNode);

		// recursively assign weights by 
		calculateWeightsAbove(rootNode);
	}
	
	public static Node findChild(String name) {
		for(Node n : nodes)
			if(n.name.equals(name))
				return n;
		System.out.println("cannot find node named " + name);
		return null;
	}
	
	public static int calculateWeightsAbove(Node node) {
		List<Integer> seenWeights = new ArrayList<>();
		int weightAbove = 0;
		for(Node n : node.children) {
			int childWeight = calculateWeightsAbove(n) + n.weight;
			seenWeights.add(childWeight);
			weightAbove += childWeight;
		}
		
		node.weightAbove = weightAbove;
		
		boolean allEqual = seenWeights.stream().distinct().limit(2).count() <= 1;
		if(!allEqual) {
			System.out.println("Node " + node.name + " is unbalanced!");
			for(Integer i : seenWeights) System.out.print(i.intValue() + " ");
			System.out.println();
			
			System.out.println(node.name + "'s weight above is " + weightAbove + " has children:");
			for(Node c : node.children) {
				System.out.println("\t" + c.name + " " + c.weight + " weight above " + c.weightAbove + " total " + (c.weightAbove + c.weight));
			}
			System.out.println();
		}
		
		return weightAbove;
	}
	
	// Put this node's children into its list
	public static void assemble(Node node) {
		for(String childName : node.childrenStrings) {
			Node child = findChild(childName);
			node.children.add(child);
			nodes.remove(child);
		}
		
		node.childrenStrings.clear();
		
		for(Node n : node.children) {
			assemble(n);
		}
	}
	
	static class Node {
		
		String name;
		int weight;
		int weightAbove  = 0;
		boolean isBalanced = true;
		Node parent;
		List<Node> children = new ArrayList<>();
		List<String> childrenStrings = new ArrayList<>();
		
		public Node(String name, int weight) {
			this.weight = weight;
			this.name = name;
		}
	}
	
	/*
	SAMPLE OUTPUT
  --------
	 	svugo 32
		Node yruivis is unbalanced!
		2671 2671 2680 
		yruivis's weight above is 8022 has children:
			oxipms 2533 weight above 138 total 2671
			ggpau 91 weight above 2580 total 2671
			sphbbz 1161 weight above 1519 total 2680
		
		Node gjxqx is unbalanced!
		10782 10773 10773 10773 10773 10773 
		gjxqx's weight above is 64647 has children:
			yruivis 2760 weight above 8022 total 10782
			rizjob 6366 weight above 4407 total 10773
			qsfwl 63 weight above 10710 total 10773
			asckjlv 4889 weight above 5884 total 10773
			sfqwrge 948 weight above 9825 total 10773
			bncdhrm 3810 weight above 6963 total 10773
		
		Node svugo is unbalanced!
		64652 64661 64652 64652 64652 
		svugo's weight above is 323269 has children:
			xolvnpy 22946 weight above 41706 total 64652
			gjxqx 14 weight above 64647 total 64661
			gtzxxav 8936 weight above 55716 total 64652
			njorjq 31504 weight above 33148 total 64652
			qpiklvf 11870 weight above 52782 total 64652
		--------
	*/
	
	/*
	 * yruivis's child sphbbz weights 2680, which is 9 above 2671.
	 * sphbbz must go from weight 1161 to 1152 in order to balance yruivis's disc
	 * the answer to AoC7 part 2 is therefore 1152.
	 * 
	 * the output shows all trees that are unbalanced, where svugo is the root.
	 * you can trace the path to the unbalanced node!
	 */
}