VB.NET 排列组合算法实现

最新推荐文章于 2023-02-26 20:24:29 发布

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最新推荐文章于 2023-02-26 20:24:29 发布

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文章标签： c#

本文介绍了一种用于生成给定数组中所有可能组合的算法，并提供了VB.NET和C#的实现代码。该算法能够处理任意数量的不重复元素，通过递归方式枚举所有可能的组合形式。

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假设给定数组 A[ ] ， A中元素不重复，要求出所有元素的组合：

A[a, b, c]

→ a

→ b

→ c

→ a b

→ a c

→ b c

→ a b c

' 求给定数组，n个元素进行组合的枚举结果。 ' n=1时，组合个数为1，如：a； ' n=2时，组合个数为2，如：ab； ' n=3时，组合个数为3，如：abc； Function Comb(ByVal arr As List(Of String), ByVal n As Integer) As List(Of String) Dim newArray As List(Of String) = New List(Of String) If n = 1 Then newArray = arr ElseIf n = 2 Then For i As Integer = 0 To arr.Count - 1 For j As Integer = i + 1 To arr.Count - 1 newArray.Add(arr(i) & "&" & arr(j)) Next Next Else Dim str As String = "" For i As Integer = 0 To arr.Count - 1 str = arr(i) Dim tempArr As List(Of String) = New List(Of String) For j As Integer = i + 1 To arr.Count - 1 tempArr.Add(arr(j)) Next If tempArr.Count < n - 1 Then Exit For End If Dim arr1 As List(Of String) = Comb(tempArr, n - 1) For Each strTemp As String In arr1 newArray.Add(str & "&" & strTemp) Next Next End If Return newArray End Function

使用：

Sub Main() '使用例： '构造一个数组： Dim arrList As List(Of String) = New List(Of String) From {"a", "b", "c"} For i As Integer = 1 To arrList.Count Dim lstResult As List(Of String) = Comb(arrList, i) For Each str As String In lstResult Console.WriteLine(str) Next Next Console.Read() End Sub
数组："a", "b", "c", "d"

输出结果：

a
b
c
d
a&b
a&c
a&d
b&c
b&d
c&d
a&b&c
a&b&d
a&c&d
b&c&d
a&b&c&d

C# 版本的：

public static IEnumerable<string> Comb(string chars) { var data = chars.ToCharArray(); var result = new[] {""}; for(var i=0; i<chars.Length; i++) { result = (from a in data from b in result where !b.Contains(a) select a + "" + b).ToArray(); } return result; }输入： abcd
输出：

abc
acb
bac
bca
cab
cba