如何实现链表快速排序？（大部分代码已完成）

Question

我在visual basic中实现链表快速排序时遇到了一些困难，问题是典型的堆栈溢出。由于它是一个递归算法，我认为它是我所缺少的相当简单的东西，但我已经盯着它看了好几个小时，在纸上跟踪它-它将永远只工作在三个或更少的项目，有时四个。任何帮助都将不胜感激。

我所遵循的算法是

1. 从列表中选择一个称为透视的元素。
2. 对列表重新排序，使所有值小于透视的元素都在透视之前，而所有值大于透视的元素都在透视之后（相等的值可以从任何一个方向移动）。分区后，枢轴处于其最终位置。这称为分区操作。
3. 将上述步骤递归应用于具有较小值的元素子列表，并单独应用于具有较大值的元素子列表。

变量“countabc”保存列表中的项目数。

下面是node类的代码：

Public Class Node
    'Each node contains the values for one value and is stored 
    'in the dynamic linked list.
    Public Name As String
    Public NextNode As Node
    Public PKey As Integer
    Public Sub New()
        'Initializes a new node
        Name = ""
        NextNode = Nothing
        PKey = 0
    End Sub
End Class
Public start As Node
Public Sub New()
    'Initializes a new linked list by setting start as the first node
    start = New Node
End Sub

对于添加例程：

Public Sub AddABC(ByVal Name As String, ByVal PKey As Integer)
    'Adds items to a dynamic linked list ordered in alphabetical order
    Dim NewNode As New Node
    Dim ptr As Node = start.NextNode
    Dim prev As Node = start
    NewNode.PKey = PKey
    While ptr IsNot Nothing AndAlso ptr.Name < NewNode.Name
        prev = ptr
        ptr = ptr.NextNode
    End While
    NewNode.Name = Name
    NewNode.NextNode = ptr
    prev.NextNode = NewNode
    countABC += 1
End Sub

和排序所需的两个函数（连接列表用于级联）

Public Function SortAlphabetically() As AllColumns
    'This is a quicksort routine that creates a new linked list 
    '(that is not saved) in alphabetical order
    If countABC > 1 Then
        Dim pivotPkey As Integer = Math.Ceiling(countABC / 2)
        Dim pivot As New Node
        Dim ptr As Node = start.NextNode

        While ptr IsNot Nothing
            If ptr.PKey = pivotPkey Then
                pivot = ptr
            End If
            ptr = ptr.NextNode
        End While

        Dim lower As New AllColumns
        Dim higher As New AllColumns

        ptr = start.NextNode

        While ptr IsNot Nothing
            If ptr.Name < pivot.Name Then
                lower.AddABC(ptr.Name, ptr.PKey)
            Else
                higher.AddABC(ptr.Name, ptr.PKey)
            End If
            ptr = ptr.NextNode
        End While

        Return (Joinlists(lower.SortAlphabetically, pivot, 
                                         higher.SortAlphabetically))

    Else
        Return Me
    End If
End Function

Private Function Joinlists(ByVal lower As AllColumns, 
                           ByVal pivot As Node, 
                           ByVal higher As AllColumns) As AllColumns
    'Joins two dynamic linked lists together with a pivot value 
    'separating them
    Dim list As AllColumns = lower
    list.AddABC(pivot.Name, pivot.PKey)

    Dim ptr As Node = higher.start.NextNode

    While ptr IsNot Nothing
        list.AddABC(ptr.Name, ptr.PKey)
        ptr = ptr.NextNode
    End While
    Return list

End Function

感谢阅读，我希望我已经很好地解释了这个问题，没有遗漏任何东西（这是可能的，因为它是一个更大的程序的一部分）。

编辑

下面是完整的类定义和第一个子，希望能更好地解释它：

Public Class AllColumns
Public countABC As Integer = 0
Public Class Node
    'Each node contains the values for one value and is stored in the dynamic linked list.
    Public Name As String
    Public NextNode As Node
    Public PKey As Integer
    Public Sub New()
        'Initialises a new node
        Name = ""
        NextNode = Nothing
        PKey = 0
    End Sub
End Class

Public start As Node

Public Sub New()
    'Initialises a new linked list by setting start as the first node
    start = New Node
    countABC = 0
End Sub

当lower和higher被声明为“new allColumns”时，它们不是有自己的countABC值吗？

我不认为例程是导航到pivot然后排序它后面的所有值，例程的这一部分才是实际排序，“ptr”被设置为“start.nextnode”IE。事前列表中的第一项。

 ptr = start.NextNode

    While ptr IsNot Nothing
        If ptr.Name < pivot.Name Then
            lower.AddABC(ptr.Name, ptr.PKey)
        Else
            higher.AddABC(ptr.Name, ptr.PKey)
        End If
        ptr = ptr.NextNode
    End While

    Return (Joinlists(lower.SortAlphabetically, pivot, 
                                     higher.SortAlphabetically))

我应该先说得更清楚一点，道歉。

Answer 1

Public Function SortAlphabetically() As AllColumns
    'This is a quicksort routine that creates a new linked list 
    '(that is not saved) in alphabetical order
    If countABC > 1 Then
        ...
        Return (Joinlists(lower.SortAlphabetically, pivot, 
                                         higher.SortAlphabetically))

countabc似乎是全局节点计数，而不是当前排序的子节的节点计数，因此该条件总是为真，因此将有无限次递归。

还有，start到底是从哪里来的（它是从哪里更新的）？

最后，在我看来，您是导航到pivot节点，然后根据比较添加到左侧和右侧子列表，但是pivot之前的节点呢？