N皇后问题 C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace nQueenDi1ci
{
    class NQueen
    {
        private int n;   //皇后的个数
        int[] x;            //当前解
        long sum;      //可行方案个数

        public long nQueen(int nn)
        {
            this.n = nn;
            sum = 0;
            x = new int[n + 1];
            for (int i = 0; i < n + 1; i++)
            {
                x[i] = 0;     //首先初始化
            }
            BackTrack(1);
            return sum;
        }

        public bool IsSuitablePlace(int k)
        {
            for (int j = 1; j < k; j++)
            {
                if ((Math.Abs(k - j) == Math.Abs(x[j] - x[k]))
                    || (x[j] == x[k]))
                {
                    return false;
                }
            }
            return true;
        }

        public void BackTrack(int t)
        {
            if (t > n)
            {
                sum++;
            }
            else
            {
                for (int i = 1; i < n + 1; i++)
                {
                    x[t] = i;
                    if (IsSuitablePlace(t) == true)
                    {
                        BackTrack(t + 1);
                    }
                }
            }
        }

        public long GetSum()
        {
            return sum;
        }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace nQueenDi1ci
{
    class Program
    {
        static void Main(string[] args)
        {
            NQueen q = new NQueen();
            q.nQueen(4);
            Console.WriteLine(q.GetSum());
            Console.Read();

        }
    }
}