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计算机等级考试二级VB常用算法:排序
作者:佚名  文章来源:不详  点击数  更新时间:2008/4/18 14:45:54  文章录入:杜斌  责任编辑:杜斌

  1、算法说明
  1)选择法排序  
    (1)从n个数中选出最小数的下标,出了循环,将最小数与第一个数交换位置;
    (2)除第一个数外,在剩下的n-1个数中再按方法(1)选出次小的数,与第二个数交换位置;
    (3)以此类推,最后构成递增序列。
    譬如:
                                                8       6       9       3       2       7
    第一轮交换后             2       6       9       3       8       7
    第二轮交换后             2       3       9       6       8       7
    第三轮交换后             2       3       6       9       8       7
    第四轮交换后             2       3       6       7       8       9
    第五轮无交换             2       3       6       7       8       9
     
    程序代码如下:
    Private Sub xzPaiXu(a() As Double, sheng As Boolean)
        'a为需要排序的数组,sheng为True则为升序排列,为False,则为降序排列。
        Dim i As Integer, j As Integer
        Dim temp As Double
        Dim m As Integer
        For i = LBound(a) To UBound(a) - 1     '进行数组大小-1轮比较
            m = i                              '在第i轮比较时,假定第
                                               'i个元素为最值元素
            For j = i + 1 To UBound(a)         '在剩下的元素中找出最
                                               '值元素的下标并记录在m中
                If sheng Then                  '若为升序,则m记录最小元素
                                               '下标,否则记录最大元素下标
                    If a(j) < a(m) Then m = j
                Else
                    If a(j) > a(m) Then m = j
                End If
            Next j                             '将最值元素与第i个元素交换
            temp = a(i)
            a(i) = a(m)
            a(m) = temp
        Next i
    End Sub
     
    调用该过程示例:
    Option Base 1
    Private Sub Command1_Click()
        Dim b(6) As Double
        b(1) = 8
        b(2) = 6
        b(3) = 9
        b(4) = 3
        b(5) = 2
        b(6) = 7
        Call xzPaiXu(b, True)
        For i% = 1 To 6
            Print b(i)
        Next
    End Sub

  2)冒泡法排序
    选择排序法在每一轮排序时找最值元素的下标,出了内循环(一轮排序结束),再交换最小数的位置;而冒泡法在每一轮排序时将相邻的数比较,当次序不对就交换位置,出了内循环,最值数已经冒出。
    譬如:
                                        8       6       9       3       2       7
    8  6  9  3  2  7
    8  6  9  2  3  7
    8  6  2  9  3  7
    8  2  6  9  3  7
    2  8  6  9  3  7
                                        ….
                                       2  3  8  6  9  7
                                       ….
                                       2  3  6  8  7  9
                                       ….
                                       2  3  6  7  8  9
    ….
    2  3  6  7  8  9
     
    程序代码如下: 
    Private Sub mpPaiXu(a() As Double, sheng As Boolean)
        'a为需要排序的数组,sheng为True则为升序排列,为False,则为降序排列。
        Dim i As Integer, j As Integer
        Dim temp As Double
        Dim m As Integer
        For i = LBound(a) To UBound(a) - 1     '进行n-1轮比较
           
            For j = UBound(a) To i + 1 Step -1 '从n到i个元素两两进行比较
                                              
                If sheng Then                  '若次序不对,马上进行交换
                                              
                    If a(j) < a(j - 1) Then
                        temp = a(j)
                        a(j) = a(j - 1)
                        a(j - 1) = temp
                    End If
                Else
                    If a(j) > a(j - 1) Then
                        temp = a(j)
                        a(j) = a(j - 1)
                        a(j - 1) = temp
                    End If
                End If
            Next j                             '出了内循环,一轮排序结束
                                               '最值元素冒到最上边
        Next i
    End Sub 
     
    调用该过程代码基本同上。

    2、实战练习
  1)补充代码(2003秋二(10))
  下面是一个采用拉锯式排序法对数组元素按升序进行排序的程序,所谓“拉锯式排序法”是这一遍把最小的元素从下到上送到最上的位置,下一遍则是从上到下把最大的元素送到最下的位置。
     
     
                      Option Base 1
                      Private Sub Command1_Click()
                      Dim a(10) As Integer,i As Integer
                    For i = 1 To 10
                       a(i) = Int(Rnd * 10)+1
                       Text1 = Text1 & Str(a(i))
                    Next i
                    Call shaker_sort(a)
                    For i = 1 To 10
                       Text2 = Text2 & Str(a(i))
                    Next i
                      End Sub
     
     
                      Private Sub Shaker_sort(k() As Integer)
                      Dim i As Integer,c As Integer,d As Integer
                      Dim t As Integer
                      c = 1
                      d =     (1) 
                      Do
                          For     (2)    Step-1
                             If k(i=1)>k(i) Then
                                t = k(i-1):k(i-1) = k(i):k(i) = t
                             End If
                          Next i
                              (3) 
                          For i = c+1 To d
                             If     (4) Then
                                t = k(i-1):k(i-1) = k(i):k(i) = t
                             End If
                          Next i
                          d = d-1
                      Loop While     (5) 
                      End Sub

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