とりあえず（？）作ってみた。（手荷物一時預かり 編）その３。

東方算程譚:手荷物一時預かり
まずはsetの用意。これが間違ってたらアウトですなぁ。

Imports System

Imports System.Collections.Generic


Public Class [Set](Of T As System.IComparable)


  Private _list As SortedList(Of T, Boolean)


  Public ReadOnly Property Empty() As Boolean

    Get

      Return Me._list.Count = 0

    End Get

  End Property


  Public Sub New()
    Me._list = New SortedList(Of T, Boolean)()
  End Sub


  Public Function Find(ByVal key As T) As Iterator
    Dim result As New Iterator(Iterator.Mode.Normal, Me._list)
    Dim index As Integer = Me._list.IndexOfKey(key)
    If index = -1 Then
      Return Me.End
    Else
      result += (index + 1)
    End If
    Return result
  End Function


  Public Function Insert(ByVal t As T) As Boolean
    Try
      Me._list.Add(t, False)
    Catch ex As ArgumentException
      Return False
    End Try
    Return True
  End Function


  Public Sub Clear()
    Me._list.Clear()
  End Sub


  Public Function Erace(ByVal value As T) As Boolean
    Return Me._list.Remove(value)
  End Function


  Public Function Begin() As Iterator
    Dim result As New Iterator(Iterator.Mode.Normal, Me._list)
    result += 1
    Return result
  End Function


  Public Function [End]() As Iterator
    Dim result As New Iterator(Iterator.Mode.Normal, Me._list)
    result += Me._list.Count
    result += 1
    Return result
  End Function


  Public Function RBegin() As Iterator
    Dim result As New Iterator(Iterator.Mode.Reverse, Me._list)
    result += 1
    Return result
  End Function


  Public Function REnd() As Iterator
    Dim result As New Iterator(Iterator.Mode.Reverse, Me._list)
    result += Me._list.Count
    result += 1
    Return result
  End Function


  Public Class Iterator
    Enum Mode As Integer
      Normal = 1

      Reverse = -1
    End Enum


    Private _mode As Mode
    Private _list As SortedList(Of T, Boolean)
    Private _index As Integer
    Public Property Index() As Integer

      Get

        Return _index

      End Get

      Set(ByVal value As Integer)

        _index = value

        If _index < 0 Then

          _index = -1

        End If

        If _index > Me._list.Count - 1 Then

          _index = Me._list.Count

        End If

      End Set

    End Property

    
    Public Sub New()
      Me._mode = [Set](Of T).Iterator.Mode.Normal

      Me._list = New SortedList(Of T, Boolean)
    End Sub


    Public Sub New(ByVal mode As Mode, ByVal list As SortedList(Of T, Boolean))
      Me._mode = mode

      Me._list = list
      Reset()
    End Sub


    Public Sub Reset()
      If Me._mode = Iterator.Mode.Normal Then
        Index = -1
      Else
        Index = Me._list.Count
      End If
    End Sub


    Public Property Current() As T

      Get

        Return Me._list.Keys(Index)

      End Get

      Set(ByVal value As T)

        Me._list.Add(value, False)

      End Set

    End Property


    Public Overloads Sub Resize(ByVal n As Integer)
      Me.Resize(n, Nothing)
    End Sub


    Public Overloads Sub Resize(ByVal n As Integer, ByVal t As T)
      If Me._list.Count >= n Then
        Exit Sub
      End If
      For i As Integer = 0 To (n - Me._list.Count) - 1
        Me._list.Add(t, False)
      Next
    End Sub




    Public Function MoveNext() As Boolean
      If Me._mode = Iterator.Mode.Normal Then
        If Index = Me._list.Count - 1 Then
          Return False
        End If
      Else
        If Index = 0 Then
          Return False
        End If
      End If
      Index += Me._mode
      Return True
    End Function


    Public Shared Operator +(ByVal target As Iterator, ByVal n As Integer) As Iterator
      target.Index += (target._mode * n)
      Return target
    End Operator


    Public Shared Operator -(ByVal target As Iterator, ByVal n As Integer) As Iterator
      target.Index -= (target._mode * n)
      Return target
    End Operator


  End Class


End Class