C# 1到10的数组每次取三个不能重复，有多少种组合

Question

C#  1到10的数组每次取三个不能重复，有多少种组合？{1,2,3,4,5,6,7,8,9,10}
比如1,2,3    1,2,4    1,2,5 等求算法输出

Answer 1

组合问题（从M个不同字符中任取N个字符的所有组合）思路：状态数组，其下标表示1到m个数，数组元素的值为1，表示其下标代表的字符被选中，为0则没选中。 
首先初始化，将数组前n个元素置1，表示第一个组合为前n个数。 
然后从左到右扫描数组元素值的“10”组合，找到第一个“10”组合后将其变为“01”组合，同时将其左边的所有“1”全部移动到数组的最左端。 
当“1”全部移动到最右端时，就得到了最后一个组合。 public String[] GetAllCombination(String str,Int32 n)  //n < str.Length 
        {
            Int32[] state = new Int32[str.Length];
            Char[] chars = str.ToCharArray();
            List<String> list = new List<String>();            for (Int32 i = 0; i < n; i++)
            {
                state[i] = 1;
            }
            for (Int32 i = n; i < state.Length; i++)
            {
                state[i] = 0;
            }            list.Add(str.Substring(0,n));
            while (true)
            {
                Boolean flag = true;
                Int32 index = 0;
                Int32 oneCount = 0;
                Int32 zeroCount = 0;
                StringBuilder sbuilder = new StringBuilder();                for(; index < state.Length - 1; index++)
                {
                    if (state[index] == 1 && state[index + 1] == 0)
                    {
                        Int32 temp = state[index];
                        state[index] = state[index + 1];
                        state[index + 1] = temp;
                        break;
                    }
                }                for (Int32 i = 0; i < index; i++)
                {
                    if (state[i] == 0)
                        zeroCount++;
                    else
                        oneCount++;
                }                for (Int32 i = 0; i < index; i++)
                {
                    if (i < oneCount)
                        state[i] = 1;
                    else
                        state[i] = 0;
                }                for (Int32 i = 0; i < chars.Length; i++) 
                {
                    if (state[i] == 1)
                        sbuilder.Append(chars[i]);
                }                list.Add(sbuilder.ToString());                for (Int32 i = 0; i < chars.Length - n; i++)
                {
                    if (state[i] == 1)
                    {
                        flag = false;
                        break;
                    }
                }
                if (flag)
                    break;
            }            return list.ToArray();
        }
我的是输入一个字符串，和一个数字，比如 "abcde" 3, 然后会输出3个字母的全部组合,你稍微修改下就可以了from my blog
http://www.cnblogs.com/Peter-Zhang/articles/1783814.html

Answer 2

Enumeralbe.Range
var r = from a in Enumerable.Range(1, 10)
                    from b in Enumerable.Range(1,10)
                    from c in Enumerable.Range(1,10)
http://topic.csdn.net/u/20090217/21/F41ED9F6-F929-451C-A5C9-80D2E408422A.html

Answer 3

class Program
    {
        static int[] numlist = new int[10] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
        static void Main(string[] args)
        {
            int num = 0;
            string nunstr = "";
            for (int i = 0; i < numlist.Length-2; i++)
            {
                for (int j = i + 1; j < numlist.Length - 1; j++)
                {
                    nunstr = numlist[i] + "," + numlist[j] + "," + numlist[j + 1];
                    num++;
                    Console.WriteLine(nunstr);
                }
            }
            Console.WriteLine(num.ToString());
        }
    }

Answer 4

少了一个循环
static int[] numlist = new int[10] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
        static void Main(string[] args)
        {
            int num = 0;
            string nunstr = "";
            for (int i = 0; i < numlist.Length-2; i++)
            {
                for (int j = i + 1; j < numlist.Length - 1; j++)
                {
                    for (int k = i + 2; k < numlist.Length; k++)
                    {
                        nunstr = numlist[i] + "," + numlist[j] + "," + numlist[k];
                        num++;
                        Console.WriteLine(nunstr);
                    }
                }
            }
            Console.WriteLine(num.ToString());
        }

Answer 5

public static String[] GetAllCombination(Int32[] arr, Int32 n)  //n < str.Length 
        {
            Int32[] state = new Int32[arr.Length];
            List<String> list = new List<String>();            for (Int32 i = 0; i < n; i++)
            {
                state[i] = 1;
            }
            for (Int32 i = n; i < state.Length; i++)
            {
                state[i] = 0;
            }            String str = "";
            for(Int32 i = 0;i < n;i++)
                str += arr[i] + ",";            list.Add(str.TrimEnd(','));            while (true)
            {
                Boolean flag = true;
                Int32 index = 0;
                Int32 oneCount = 0;
                Int32 zeroCount = 0;
                StringBuilder sbuilder = new StringBuilder();                for (; index < state.Length - 1; index++)
                {
                    if (state[index] == 1 && state[index + 1] == 0)
                    {
                        Int32 temp = state[index];
                        state[index] = state[index + 1];
                        state[index + 1] = temp;
                        break;
                    }
                }                for (Int32 i = 0; i < index; i++)
                {
                    if (state[i] == 0)
                        zeroCount++;
                    else
                        oneCount++;
                }                for (Int32 i = 0; i < index; i++)
                {
                    if (i < oneCount)
                        state[i] = 1;
                    else
                        state[i] = 0;
                }                for (Int32 i = 0; i < arr.Length; i++)
                {
                    if (state[i] == 1)
                        sbuilder.Append(arr[i] + ",");
                }                list.Add(sbuilder.ToString().TrimEnd(','));                for (Int32 i = 0; i < arr.Length - n; i++)
                {
                    if (state[i] == 1)
                    {
                        flag = false;
                        break;
                    }
                }
                if (flag)
                    break;
            }            return list.ToArray();
        }
这回可以了

Answer 6

static void Main(string[] args)
{
    List<int> arr = new List<int>(new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 });
    StringBuilder builder = new StringBuilder();
    arr.ForEach(a1 => arr.Except(new int[] { a1 }).ToList().ForEach(a2 => arr.Except(new int[] { a1, a2 }).ToList().ForEach(a3 => builder.AppendLine(a1.ToString() + "," + a2.ToString() + "," + a3.ToString()))));
    Console.WriteLine(builder.ToString());
    File.WriteAllText("result.txt", builder.ToString());
    Console.ReadKey();
}运行后到你的程序目录下看result.txt文件，里面是结果。

Answer 7

class Program
    {
        static int[] numlist = new int[10] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
        static void Main(string[] args)
        {
            int num = 0;
            string nunstr = "";
            for (int i = 0; i < numlist.Length-2; i++)
            {
                for (int j = i + 1; j < numlist.Length - 1; j++)
                {
                    for (int k = i + 2; k < numlist.Length; k++)
                    {
                        nunstr = numlist[i] + "," + numlist[j] + "," + numlist[k];
                        num++;
                        Console.WriteLine(nunstr);
                    }
                }
            }
            Console.WriteLine(num.ToString());
        }
    }

Answer 8

想由哪些组成就修改这个List就可以了。
List<int> arr = new List<int>(new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 });

Answer 9

public static String[] GetAllCombination(Int32[] arr, Int32 n)  //取n个的组合 
        {
            Int32[] state = new Int32[arr.Length];
            List<String> list = new List<String>();            for (Int32 i = 0; i < n; i++)
            {
                state[i] = 1;
            }
            for (Int32 i = n; i < state.Length; i++)
            {
                state[i] = 0;
            }            String str = "";
            for(Int32 i = 0;i < n;i++)
                str += arr[i] + ",";            list.Add(str.TrimEnd(','));            while (true)
            {
                Boolean flag = true;
                Int32 index = 0;
                Int32 oneCount = 0;
                Int32 zeroCount = 0;
                StringBuilder sbuilder = new StringBuilder();                for (; index < state.Length - 1; index++)
                {
                    if (state[index] == 1 && state[index + 1] == 0)
                    {
                        Int32 temp = state[index];
                        state[index] = state[index + 1];
                        state[index + 1] = temp;
                        break;
                    }
                }                for (Int32 i = 0; i < index; i++)
                {
                    if (state[i] == 0)
                        zeroCount++;
                    else
                        oneCount++;
                }                for (Int32 i = 0; i < index; i++)
                {
                    if (i < oneCount)
                        state[i] = 1;
                    else
                        state[i] = 0;
                }                for (Int32 i = 0; i < arr.Length; i++)
                {
                    if (state[i] == 1)
                        sbuilder.Append(arr[i] + ",");
                }                list.Add(sbuilder.ToString().TrimEnd(','));                for (Int32 i = 0; i < arr.Length - n; i++)
                {
                    if (state[i] == 1)
                    {
                        flag = false;
                        break;
                    }
                }
                if (flag)
                    break;
            }            return list.ToArray();
        }
        static void Main(string[] args)
        {
            Int32[] arr = { 1, 2, 3, 4, 5,6,7,8,9,10 };
            String[] list = GetAllCombination(arr, 3);
            foreach (String s in list)
                Console.WriteLine(s);
        }
修改的，取你的{1,2,3,4,5,6,7,8,9,10} 3个数的组合输出：
1,2,3
1,2,4
1,3,4
2,3,4
1,2,5
1,3,5
2,3,5
1,4,5
2,4,5
3,4,5
1,2,6
1,3,6
2,3,6
1,4,6
2,4,6
3,4,6
1,5,6
2,5,6
3,5,6
4,5,6
1,2,7
1,3,7
2,3,7
1,4,7
2,4,7
3,4,7
1,5,7
2,5,7
3,5,7
4,5,7
1,6,7
2,6,7
3,6,7
4,6,7
5,6,7
1,2,8
1,3,8
2,3,8
1,4,8
2,4,8
3,4,8
1,5,8
2,5,8
3,5,8
4,5,8
1,6,8
2,6,8
3,6,8
4,6,8
5,6,8
1,7,8
2,7,8
3,7,8
4,7,8
5,7,8
6,7,8
1,2,9
1,3,9
2,3,9
1,4,9
2,4,9
3,4,9
1,5,9
2,5,9
3,5,9
4,5,9
1,6,9
2,6,9
3,6,9
4,6,9
5,6,9
1,7,9
2,7,9
3,7,9
4,7,9
5,7,9
6,7,9
1,8,9
2,8,9
3,8,9
4,8,9
5,8,9
6,8,9
7,8,9
1,2,10
1,3,10
2,3,10
1,4,10
2,4,10
3,4,10
1,5,10
2,5,10
3,5,10
4,5,10
1,6,10
2,6,10
3,6,10
4,6,10
5,6,10
1,7,10
2,7,10
3,7,10
4,7,10
5,7,10
6,7,10
1,8,10
2,8,10
3,8,10
4,8,10
5,8,10
6,8,10
7,8,10
1,9,10
2,9,10
3,9,10
4,9,10
5,9,10
6,9,10
7,9,10
8,9,10