学进去

给出n个不重复的介于区间[-10，10]的整数（n≤10），查找区间中未出现的正整数。
例如：

按上述要求，编写一个VB程序：在文本框Text1中输入n个整数（逗号分隔并以逗   号结尾），单击“查找”按钮Command1，在标签Label2中输出查找结果。程序运行界面如图所示。

（1）对从输入字符串中提取的n个整数排序：将其中的正整数进行升序排序，排序后正整数在前，其它的在后。以图中数据为例（10，3，-2，0，-6，6，-5，2，）提取整数，采用如下程序的选择排序算法，所需的交换次数为______次。
（2）请在划线处①②③填入合适的代码。
Private Sub Command1_Click()
Dim i As Integer, j As Integer, n As Integer, k As Integer
Dim ch As String, res As String, t1 As String, t2 As Integer
Dim m As Integer         'm记录正整数的个数
Dim a(1 To 10) As Integer
s = Text1.Text
n = 0
For i = 1 To Len(s)'提取整数,并保存在数组a中
ch = Mid(s, i, 1)
If ch = "," Then
n = n + 1
a(n) = Val(t1)
t1 = ""
Else
t1 = t1 + ch
End If
Next i
For i = 1 To n – 1
k = i
For j = i + 1 To n
If a(j) > 0 Then
If ________ Then k = j
End If
Next j
If k <> i Then
t2 = a(k): a(k) = a(i): a(i) = t2
End If
If _______ Then
m = i   'm记录正整数的个数
Else
Exit For
End If
Next i
For i = m To 1 Step -1
_____ 
Next i
For i = 1 To 10
If a(i) <> i Then res = res + Str(i) + ","
Next i
Label2.Caption = res
End Sub