day7.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace Day7
{
    public class Node
    {
        public string Name { get; set; }
        public int Weight { get; set; }
        public Node Parent { get; set; }
        public string[] ChildNames { get; set; }
        public List<Node> Children { get; } = new List<Node>();

        public int TotalWeight()
        {
            return Weight + Children.Sum(c => c.TotalWeight());
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var reports = File.ReadLines("input.txt").Select(l =>
            {
                var parts = l.Split(' ', 4);
                return new { name = parts[0], weight = parts[1], supports = parts.Length > 2 ? parts[3].Split(new char[] { ',', ' ' }, StringSplitOptions.RemoveEmptyEntries) : null, parts };
            });

            var nodes = reports.Select(r => new Node { Name = r.name, Weight = int.Parse(r.weight.Substring(1,r.weight.Length-2)), ChildNames = r.supports }).ToList();
            nodes.ForEach(n => {
                n.Parent = nodes.FirstOrDefault(x => x.ChildNames != null && x.ChildNames.Contains(n.Name));
                n.Parent?.Children.Add(n);
            });
            nodes.Where(n => n.Parent == null).Select(n => n.Name).ToList().ForEach(Console.WriteLine);

            foreach (var node in nodes.Where(n => n.Children.Count > 1))
            {
                var min = node.Children.Min(c => c.TotalWeight());
                var max = node.Children.Max(c => c.TotalWeight());
                var diff = max - min;
                if (diff == 0) continue;

                var countMin = node.Children.Count(c => c.TotalWeight() == min);
                var countMax = node.Children.Count(c => c.TotalWeight() == max);

                if (countMax >= countMin)
                {
                    var n = node.Children.First(x => x.TotalWeight() == min);
                    var ow = n.Weight;
                    n.Weight += diff;
                    if (IsBalanced(nodes))
                    {
                        Console.WriteLine("New node weight: {0}", n.Weight);
                        break;
                    }
                    n.Weight = ow;
                }
                else
                {
                    var n = node.Children.First(x => x.TotalWeight() == max);
                    var ow = n.Weight;
                    n.Weight -= diff;
                    if (IsBalanced(nodes))
                    {
                        Console.WriteLine("New node weight: {0}", n.Weight);
                        break;
                    }
                    n.Weight = ow;
                }
            }
        }

        static bool IsBalanced(List<Node> nodes)
        {
            foreach (var node in nodes.Where(n => n.Children.Count > 1))
            {
                var min = node.Children.Min(c => c.TotalWeight());
                var max = node.Children.Max(c => c.TotalWeight());
                var diff = max - min;
                if (diff != 0) return false;
            }
            return true;
        }
    }
}