非递归实现不重复序列的全排列（三）

笔者曾利用进制转换实现不重复序列全排列（http://blog.csdn.net/northwolves/archive/2004/07/21/47400.aspx），但从0 循环到n^(n-1)-1,效率实在不高，经过仔细分析，发现一个另人激动的规律，详情见下表：

A BA CBA DCBA CDBA CBDA CBAD BCA DBCA BDCA BCDA BCAD BAC DBAC BDAC BADC BACD AB CAB DCAB CDAB CADB CABD ACB DACB ADCB ACDB ACBD ABC DABC ADBC ABDC ABCD 从上面表格可以看出，对于“ABCD”，假如先放好A（只有一种放法），再放B时，可以有BA，AB两种放法；再放C时，则针对BA，AB 各有3种放法（BA前，BA中，BA后），再放D时，各有4种放法。所以第一个元素排好后，第2个元素的位置可以用0，1 表示，第3个元素的位置可以用0，1 ，2表示，第n个元素的位置可以用0，1 ,2,3,...n-1表示，因而使用混合进制（笔者起的名字）可以实现数组元素的全排列。
代码如下：
Sub pailie3(ParamArray x())Dim starttime As Single, endtime As SingleDim i As Integer, j As Integer, Num As Long, n As IntegerDim ALL As New Collection, TEMP1 As Long, TEMP2 As Longn = UBound(x) + 1 '元素个数starttime = Timer '开始计时Num = 1For i = 1 To nNum = Num * i '递归计算n！NextFor i = 1 To NumSet ALL = Nothing '初始化集合allALL.Add x(0)TEMP1 = iFor j = 2 To nTEMP2 = TEMP1 Mod jTEMP1 = TEMP1 jIf TEMP2 = 0 ThenALL.Add x(j - 1) 'temp2为 0则放在最后ElseALL.Add x(j - 1), , BEFORE:=TEMP2 'temp2不为 0 则置于第temp2个元素前End IfNextFor j = 1 To nDebug.Print ALL(j) & " "; '输出NextDebug.PrintNextendtime = TimerDebug.Print "共 " & Num & " 种排列！用时 " & endtime - starttime & " 秒！"End Sub
Private Sub Command1_Click()pailie3 "a", "b", "c", "d", "e", "f", "g"End Sub

由于集合属于VARIANT类型，运算速度慢，换成数组进行同样的转换，发现确实快了很多：
Sub pailie4(ParamArray x())Dim starttime As Single, endtime As SingleDim i As Integer, j As Integer, k As Integer, Num As Long, n As IntegerDim ALL(), TEMP1 As Long, TEMP2 As Longn = UBound(x) + 1 '元素个数
starttime = Timer '开始计时Num = 1For i = 1 To nNum = Num * i '递归计算n！NextFor i = 1 To NumReDim ALL(1 To n) '初始化数组allALL(1) = x(0)TEMP1 = iFor j = 2 To nTEMP2 = TEMP1 Mod jTEMP1 = TEMP1 jIf TEMP2 = 0 ThenALL(j) = x(j - 1) 'temp2为 0则放在最后ElseFor k = j To TEMP2 + 1 Step -1ALL(k) = ALL(k - 1) ' temp2之后的元素后移一位NextALL(TEMP2) = x(j - 1) 'temp2不为 0 则置于第temp2个元素前End IfNextDebug.Print Join(ALL, " ") '输出Nextendtime = TimerDebug.Print "共 " & Num & " 种排列！用时 " & endtime - starttime & " 秒！"End SubPrivate Sub Command1_Click()pailie4 "a", "b", "c", "d", "e", "f", "g"End Sub
如果用COPYMEMORY进行数组的移动，速度应该更快，大家有兴趣不妨一试。