5. 判断数独状态

题目：

写程序判断一个9*9的数字盘面是否为合法的数独（查看定义）。

9*9的盘面按照Row-major order表示为一个81维的一维数组。

提示：请直接在一维数组上操作，不要先将一维数组拷贝到9*9的二维数组。

Code:

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

namespace Sudoku
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] intArr = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 2, 3, 4, 5, 6, 7, 8, 9, 1, 3, 4, 5, 6, 7, 8, 9, 1, 2, 4, 5, 6, 7, 8, 9, 1, 2, 3, 5, 6, 7, 8, 9, 1, 2, 3, 4, 6, 7, 8, 9, 1, 2, 3, 4, 5, 7, 8, 9, 1, 2, 3, 4, 5, 6, 8, 9, 1, 2, 3, 4, 5, 6, 7, 9, 1, 2, 3, 4, 5, 6, 7, 8};
            Console.WriteLine(IsSudoku(intArr));
        }

        static bool IsSudoku(int[] intArr)
        {
            int n = (int)(Math.Sqrt(intArr.Length));
            if (n * n != intArr.Length)
            {
                throw new Exception("Intput array is not meet requirement: Length doesn't equals n*n.");
            }
            Hashtable ht = new Hashtable();
            int count = 0;
            int sum = 45; //from 1 to 9, sum is 45;
            for (int i = 0; i < n; i++)
            {
                for (int j = i * n; j < i * n + n; j++)
                {
                    if (ht[intArr[j]]== null)
                    {
                        ht.Add(intArr[j], true);
                        count += intArr[j];
                    }
                    else
                    {
                        return false;
                    }
                }
                if (count != sum)
                {
                    return false;
                }
                count = 0;
                ht.Clear();
            }
            for (int i = 0; i<n; i++)
            {
                for (int j = i; j < n*n; j=j+n)
                {
                    if (ht[intArr[j]] == null)
                    {
                        ht.Add(intArr[j], true);
                        count += intArr[j];
                    }
                    else
                    {
                        return false;
                    }
                }
                if (count!=sum)
                {
                    return false;
                }
                count = 0;
                ht.Clear();
            }
            return true;
        }
    }
}