30. 使用LotusScript排序

╰半夏微凉° 2022-03-31 11:42 184阅读 0赞

排序是计算机编程中最常见的任务之一，排序算法也是最基本和常用的算法。存在许多种排序算法，它们的效率和复杂性各不相同。在LotusNotes中，公式语言里有@Sort函数，对List排序。LotusScript里没有类似的可以用作容器的数据结构，也就没有提供针对它们的排序功能。另外，使用LotusScript开发时，主要的数据对象是NotesDocument，而它们的排序都已经在视图里完成了，所以需要排序的情况并不多。但是有时候，我们也会遇到排序的需求，比如针对列表字段里的多值或是没有存在于文档中的数据。这时就需要我们在LotusScript里实现排序算法。这并不是特别困难的事，不过如果你想省事（像我一样），也可以使用现成的代码，比如下面的这几个用于排序的函数就来自于LotusNotes自带的模版数据库：

Public Function QuickSort(sArray As Variant) As Variant
    	Dim sA() As String    
    	Dim j As Long
    	Dim bottom As Long
    	Dim top As Long
    	Dim vA As Variant
    	
    	bottom = LBound ( sArray )
    	top = UBound ( sArray )
    	ReDim sA( bottom To top ) As String     
    	For j = bottom To top
    		sA ( j ) = sArray ( j )
    	Next
         ' DoQS does a QuickSort if the Sublist is longer than 10 elements
         ' Thus, when DoQS finishes, all elements are within 10 spots of their correct location.
         ' For lists that are close to being in order, an Insertion Sort is much faster than a QuickSort, so we
         ' run through the whole thing once doing an Insertion Sort to finish tidying up the order.
    	Call DoQS( sA, bottom, top )
    	Call DoInsertSort ( sA, bottom, top )
    	ReDim vA(bottom To top) As Variant
    	For j = bottom To top
    		vA ( j ) = sA ( j )
    	Next	
    	QuickSort = vA
    End Function
    Sub DoInsertSort ( sA() As String, ByVal bottom As Long, ByVal top As Long )	
    	Dim i As Long
    	Dim x As Long
    	Dim v As String
    	Dim Found As Integer
    	For i = bottom+1 To top
    		x = i
    		v = sA (i )
    		Do While (sA(x-1) > v)
    			sA ( x ) = sA ( x-1 )
    			x = x - 1
    			If x=0 Then
    				Exit Do
    			End If
    		Loop
    		sA (x) = v
    	Next
    End Sub
    Sub DoQS( sA() As String, bottom As Long, top As Long )
         ' Called by QuickSort
    	Dim length As Long
    	Dim i As Long
    	Dim j As Long
    	Dim Pivot As Long
    	Dim PivotValue As String
    	Dim t As String
    	Dim LastSmall As Long
    	length = top - bottom + 1
    	
         ' Only do the QuickSort if the sublist is at least 10 items long
    	If length > 10 Then
              ' Pivot is chosen approx. halfway through sublist.
              ' This gives us best speed if list is almost sorted already, and is no worse than any
              ' other choice if the list is in random order.
    		Pivot = bottom + (length \ 2)   
    		
              ' Move PivotValue out of the way
    		PivotValue = sA( Pivot )
    		sA ( Pivot ) = sA ( bottom )
    		sA ( bottom ) = PivotValue
    		
              ' LastSmall is the location of the last value smaller than PivotValue
    		LastSmall = bottom
    		For i = bottom + 1 To top 
    			If sA ( i ) < PivotValue Then 
    				LastSmall = LastSmall + 1
    				t = sA ( i )
    				sA ( i ) = sA ( LastSmall )
    				sA ( LastSmall ) = t
    			End If
    		Next
    		
              ' Move the PivotValue back
    		t = sA ( LastSmall )
    		sA ( LastSmall ) = sA ( bottom )
    		sA ( bottom ) = t
    		Pivot = LastSmall
    		
              ' Now sort each side
    		Call DoQS ( sA, bottom, Pivot - 1 )
    		Call DoQS ( sA, Pivot + 1, top )
    	End If
    	
    End Sub

只需要调用QuickSort函数，它会对参数中的数组排序然后返回。它根据数组的大小采用快速排序和插入排序两种不同的算法。