组合算法实现

 1         public static void GetCombination(int source, int num, ref List<string> result, int[] temp = null)
 2         {
 3             if (temp == null)
 4             {
 5                 temp = new int[num];
 6             }
 7             if (source >= num && num >= 1)
 8             {
 9                 temp[num - 1] = source;
10 
11                 if (num == 1)
12                 {
13                     result.Add(string.Join(",", temp));
14                 }
15 
16                 GetCombination(source - 1, num - 1, ref result, temp);
17 
18                 if (source > num)
19                 {
20                     GetCombination(source - 1, num, ref result, temp);
21                 }
22 
23             }
24         }

 1  public static void GetCombination2(int source, int num, ref List<string> result, int[] temp = null)
 2         {
 3             if (temp == null)
 4             {
 5                 temp = new int[num];
 6             }
 7             for (int i = source; i >= num; i--)
 8             {
 9                 temp[num - 1] = i;
10                 if (num > 1)
11                 {
12                     GetCombination2(i - 1, num - 1, ref result, temp);
13                 }
14                 else
15                 {
16                     result.Add(string.Join(",", temp));
17                 }
18             }
19         }

1             List<string> result = new List<string>();
2             GetCombination2(5, 3, ref result);
3             foreach (var a in result)
4             {
5                 Console.WriteLine(a);
6             }