选考VB算法六PPT课件

1、选考选考VB算法算法(六六)冒泡排序2020年年1月真题月真题直接交换冒泡排序直接交换冒泡排序For i=1 to n-1For j=i+1 to nIf _ Thenk=a(i):a(i)=a(j):a(j)=kEnd IfNext jNext ia(i)a(j)优化的冒泡排序优化的冒泡排序For i=1 to n-1Flag=false For If then t=a(j):a(j)=a(j-1):a(j-1)=t Flag=true End if Next jIf nof flag then exit forNext I为了知道某轮扫描中是否存在交换操作，我们可以为每个数都准备一面旗子，

2、若相邻的数需要交换位置，则举旗示意。j=n to i+1 step -1a(j-1)a(j) 鸡尾酒冒泡排序鸡尾酒冒泡排序5(left)31264(right)31254(right)613(left)2452(left, ight)3Left=right，do while leftrigh 条件不成立，程序结束鸡尾酒冒泡排序鸡尾酒冒泡排序left = 1: right = nDo While left a(i + 1) Then t = a(i): a(i) = a(i + 1): a(i + 1) = t End If Next ipos = iright = pos For i = ri

3、ght To left + 1 Step -1 If Then t = a(i): a(i) = a(i - 1): a(i - 1) = t End IfNext ileft = pos Loopa(i - 1) a(i)pos = i练习2.分组冒泡排序。使用冒泡排序算法分别对数组奇数和偶数位置的元素按升序排序。例如将数组a = (4,20,2,40,3,50,1,30,5,10)排序成a = (1,10,2,20,3,30,4,40,5,50)Private Sub Command1_Click() Dim i As Integer, j As Integer, k As Integer

4、, t As Integer For i = 1 To i表示左边界，跳跃距离为2 For j = n To 从右向左逐个扫描 If a(j) a(j - 2) Then 跳跃式比较和交换，跳跃距离为2 t = a(j): a(j) = a(j - 2): a(j - 2) = t End If Next j Next iEnd Subn Step 2i + 2 Step -1每趟可把各组的最小值都推送出来，故只需加工(n - 1) 2趟练习3.分组冒泡排序。将数组元素分成3组（即各组元素在数组中的步长为3），各自按升序排序。例如将数组a=(4,20,300,2,40,400,3,10,100

5、,1,30,200)排序成a = (1,10,100,2,20,200,3,30,300,4,40,400)Private Sub Command2_Click() Dim i As Integer, j As Integer, k As Integer, t As Integer For i = 1 To i表示左边界，跳跃距离为3 For j = n To 从右向左逐个扫描 If a(j) a(j - 3) Then 跳跃式比较和交换，跳跃距离为3 t = a(j): a(j) = a(j - 3): a(j - 3) = t End If Next j Next iEnd Subn Step 3i + 3 Step -1练习4.分组冒泡排序。将数组元素分成m组（即各组元素在数组中的步长为m），各自按升序排序。Private Sub Command8_Click() Dim i As Integer, j As Integer, k As Integer, t As Integer Dim m As Integer m = Val(Text2.Text) For i = 1 To i表示左边界，跳跃距离为m For j = n To 从右向左逐个扫描 If a(j) a(j - m) Then 跳跃式比较和交换，跳跃距离为m t = a(j): a(j) = a(j - m)