using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        int[] blades = { 500, 530, 550, 475, 450, 525, 460, 505 };

        foreach (int blade in SortBlades(blades)) Console.WriteLine(blade);

    }

    public static int[] SortBlades(int[] blades)

    {

        blades = blades.OrderByDescending(b => b).ToArray();

​

        int[] result = new int[blades.Length];

        if (result.Length == 0) return new int[0];

        result[0] = blades[0];

        for (int i = 1; i < blades.Length - 1; i++)

        {

            // get the longest empty sequence and put the current blade to its middle index

            var sequences = new List<Sequence>();

            int tmpStartIndex = 0, tmpEndIndex = 0;

            for (int j = 1; j < result.Length; j++)

            {

                if (result[j] == 0 && result[j-1] != 0) tmpStartIndex = j;

                if (result[j] != 0 && result[j-1] == 0) tmpEndIndex = j - 1;

                else if (result[j] == 0 && j == result.Length - 1) tmpEndIndex = j;

                else tmpEndIndex = 0;

                if (tmpEndIndex != 0) sequences.Add(new Sequence() { StartIndex = tmpStartIndex, EndIndex = tmpEndIndex });

            }

            foreach (var sequence in sequences) sequence.SumOfWeightsAround = result[sequence.StartIndex - 1] + (sequence.EndIndex == result.Length - 1 ? result[0] : result[sequence.EndIndex + 1]);

            // for more longest sequences take the one with minimum surrounding blades weights

            result[sequences.OrderByDescending(s => s.EndIndex - s.StartIndex).ThenBy(s => s.SumOfWeightsAround).Select(s => (s.StartIndex + s.EndIndex) / 2).First()] = blades[i];

        }

​

        // the computation is not needed for the last blade

        result[result.Select((v, i) => new { Index = i, Value = v }).Where(e => e.Value == 0).Select(e => e.Index).First()] = blades[blades.Length - 1];

        return result;

    }

}

​

public class Sequence

{

    public int StartIndex { get; set; }

    public int EndIndex { get; set; }

    public int SumOfWeightsAround { get; set; }

}

​