C#-Code

using System;

namespace trainYourProgrammer
{
	class MainClass
	{
		static long PlaceQueens(int n, bool[,] blocked, int line) {
			if (line == n)
				return 1;
			long result = 0;
			for (int i = 0; i < n; i++) {
				if (blocked [i, line])
					continue;
				result += PlaceQueens (n, PlaceQueenAt (i, line, n, blocked), line + 1);
			}
			return result;
		}

		static long PlaceQueens(int n) {
			bool[,] blocked = new bool[n, n];
			long result = 0;
			for (int i = 0; i < n/2; i++) { //Ausnutzen der Symmetrie
				result += 2 * PlaceQueens (n, PlaceQueenAt (i, 0, n, blocked), 1);
			}
			if (n % 2 == 1)
				result += PlaceQueens (n, PlaceQueenAt (n / 2, 0, n, blocked), 1);
			return result;
		}

		static bool[,] PlaceQueenAt(int x, int y, int n, bool[,] blocked) {
			int[,] offset = {{-1,-1},{-1,0},{-1,1},{0,-1},{0,1},{1,-1},{1,0},{1,1}};
			bool[,] result = (bool[,]) blocked.Clone();
			for(int dir = 0; dir < 8; dir++) {
				int x_ = x + offset[dir, 0];
				int y_ = y + offset[dir, 1];
				while (x_ >= 0 && x_ < n && y_ >= 0 && y_ < n) {
					result[x_, y_] = true;
					x_ += offset[dir, 0];
					y_ += offset[dir, 1];
				}
			}
			return result;
		}

		static void Main(string[] args) {
			for (int i = 1; i < 14; i++) {
				Console.WriteLine ("n = " + i.ToString().PadLeft(2) + ": " + PlaceQueens(i).ToString().PadLeft(6) + " Möglichkeiten");
			}
		}
	}
}