两两组合算法-递归实现方法

count = len(len-1)/n

arr={1,2,3}

len=3

n=2

组合的个数 count = len(len-1)/2 = 3(3-1)/2 =3

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得到的组合结果为

1,2

1,3

2,3

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using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Testing

{

class Program

{

static void Main(string[] args)

{

TestDoubleComposition();

Console.ReadLine();

}

static List<string> m_list;

/// <summary>

/// 两两组合算法

/// </summary>

static void TestDoubleComposition()

{

m_list = new List<string>();

List<string> list = new List<string>();

list.Add("1");

list.Add("2");

list.Add("3");

DoubleComposition(list);

m_list.ForEach(o => {

Console.WriteLine(o);

});

}

/// <summary>

/// 两两组合算法

/// </summary>

static void DoubleComposition(List<string> arr)

{

if (arr == null || arr.Count <= 1)

return;

string str = arr.First();

arr.RemoveAt(0);

arr.ForEach(o =>

{

m_list.Add(string.Format("{0},{1}",str,o));

});

DoubleComposition(arr);

}

}

}