猜数字的算法的一个简单实现

猜数字的算法的一个简单实现，用的最简单的算法，权当编程练习。

 1     class GuessNumber
 2     {
 3         public static IEnumerable<int> Guess(Func<int, int> testHanlder)
 4         {
 5             var validNumers = Enumerable.Range(1, 9);    //有效数字范围为1-9
 6             var candicateNum = from n1 in validNumers
 7                                from n2 in validNumers
 8                                from n3 in validNumers
 9                                from n4 in validNumers
10                                where new int[] { n1, n2, n3, n4 }.Distinct().Count() == 4    //过滤掉有重复的数字
11                                select n1 * 1000 + n2 * 100 + n3 * 10 + n4;
12 
13             while (true)
14             {
15                 var num = candicateNum.First();
16                 yield return num;
17 
18                 var result = testHanlder(num);
19                 if (result == 40)
20                     yield break;
21 
22                 candicateNum = candicateNum.Where(i => Test(i, num) == result);
23             }
24         }
25 
26         public static IEnumerable<int> Guess(int num)
27         {
28             return Guess(i => Test(i, num));
29         }
30         
31         //为了简单返回值为int型，如2A1B则返回21
32         public static int Test(int num1, int num2)
33         {
34             var value1 = num1.ToString("0000");
35             var value2 = num2.ToString("0000");
36 
37             Contract.Assume((value1.Length == 4) && (value2.Length == 4));
38 
39             var query = value1.Zip(value2, (ch1, ch2) => new 
40                                     {
41                                         MatchA = (ch1 == ch2),
42                                         MatchB = (ch1 != ch2) && (value1.Contains(ch2))
43                                     }).ToArray();
44 
45             var aCount = query.Count(i => i.MatchA);
46             var bCount = query.Count(i => i.MatchB);
47 
48             return aCount * 10 + bCount;
49         }
50     }