Combine whole integer array into a number called 'x'. Sort the given array so that 'x' is maximum value. This solution using brute-force approach O(n!).

MaximumValueSort.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;

namespace TestCS
{
	class Program
	{
		static void Main(string[] args) {
		
			#region Main Block
			int n = int.Parse(Console.ReadLine());
			if (n > 10 || n < 0) {
				n = 10;
			}
			string tstr = Console.ReadLine();
			List<int> list = tstr.Split(' ').Select(Int32.Parse).ToList();
			List<int> resList = Solve(list.ToArray());
			foreach (var x in resList) {
				Console.Write("{0} ", x);
			}
			Console.WriteLine();
			#endregion

			Console.ReadKey();
		}

		private static List<int> Solve(int[] arr) {
			List<int> res = new List<int>();
			Array.Sort(arr);
			BigInteger max = -1;
			while (NextPermutation(arr)) {
				BigInteger t = ToNumber(arr);
				if (max < t) {
					max = t;
					res.Clear();
					res = arr.ToList();
				}
			}
			return res;
		}

		private static BigInteger ToNumber(int[] arr) {
			return BigInteger.Parse(string.Join(string.Empty, arr));
		}

		private static bool NextPermutation(int[] numList) {
			/*
			Knuths
			1. Find the largest index j such that a[j] < a[j + 1]. If no such index exists, the permutation is the last permutation.
			2. Find the largest index l such that a[j] < a[l]. Since j + 1 is such an index, l is well defined and satisfies j < l.
			3. Swap a[j] with a[l].
			4. Reverse the sequence from a[j + 1] up to and including the final element a[n].
			*/
			
			#region STEP 1
			var largestIndex = -1;
			for (var i = numList.Length - 2; i >= 0; i--) {
				if (numList[i] < numList[i + 1]) {
					largestIndex = i;
					break;
				}
			}
			if (largestIndex < 0) return false;
			#endregion

			#region STEP 2
			var largestIndex2 = -1;
			for (var i = numList.Length - 1; i >= 0; i--) {
				if (numList[largestIndex] < numList[i]) {
					largestIndex2 = i;
					break;
				}
			}
			#endregion

			#region STEP 3
			var tmp = numList[largestIndex];
			numList[largestIndex] = numList[largestIndex2];
			numList[largestIndex2] = tmp;
			#endregion

			#region STEP 4
			for (int i = largestIndex + 1, j = numList.Length - 1; i < j; i++, j--) {
				tmp = numList[i];
				numList[i] = numList[j];
				numList[j] = tmp;
			}
			#endregion

			return true;
		}
	}
}