protected override object SolvePart1()
{
var nodes = new List <RecursiveCircusNode>();
foreach (var line in Input)
{
var splits = line.Split(new[] { "->" }, StringSplitOptions.None);
var node = new RecursiveCircusNode
{
Name = splits[0].Split()[0],
Weight = int.Parse(splits[0].Split()[1].Trim().Trim('(', ')'), CultureInfo.InvariantCulture)
};
if (splits.Length == 2)
{
node.ChildNodes.AddRange(splits[1].Trim().Split().Select(c => c.Trim(',')).ToList());
}
nodes.Add(node);
}
var children = nodes.Where(n => n.ChildNodes.Count > 0).SelectMany(n => n.ChildNodes);
return(nodes.Single(n => !children.Contains(n.Name)).Name);
}
protected override object SolvePart2()
{
// Create all nodes.
var nodes = new List <RecursiveCircusNode>();
foreach (var line in Input)
{
var splits = line.Split(new[] { "->" }, StringSplitOptions.None);
var node = new RecursiveCircusNode
{
Name = splits[0].Split()[0],
Weight = int.Parse(splits[0].Split()[1].Trim().Trim('(', ')'), CultureInfo.InvariantCulture)
};
if (splits.Length == 2)
{
node.ChildNodes.AddRange(splits[1].Trim().Split().Select(c => c.Trim(',')).ToList());
}
nodes.Add(node);
}
// Build tree
foreach (var node in nodes)
{
foreach (var child in node.ChildNodes)
{
node.Children.Add(nodes.Single(n => n.Name == child));
}
node.Children.ForEach(n => n.Parent = node);
}
// Get root node (the only one that isn't a child to another node.
var children = nodes.Where(n => n.ChildNodes.Count > 0).SelectMany(n => n.ChildNodes);
var rootNode = nodes.Single(n => !children.Contains(n.Name));
// Traverse tree to find the faulty weight.
var currentNode = rootNode;
var lastDiff = 0;
while (currentNode != null)
{
var childWeights = currentNode.GetChildWeights();
var diff = childWeights.Distinct().Max() - childWeights.Distinct().Min();
if (diff == 0)
{
return(currentNode.Weight - lastDiff);
}
lastDiff = diff;
var unique = childWeights.Single(n => childWeights.Count(m => m == n) == 1);
currentNode = currentNode.Children.Single(n => n.GetTowerWeight() == unique);
}
return(null);
}