判断非重字符串s2(至少含2个字符)是否为s1的子集,若s2的字符按序在s1中出现,则称s2为s1的子集。例:s1="a3bcd",s2="ab",s3="ba",则s2是s1的子集,s3不是s1的子集。实现该功能的VB程序段如下:
s1 = Text1.Text : s2 = Text2.Text
i = 1 : j = 1
Do While i <= Len(s1) And j <= Len(s2)
If Mid(s1, i, 1) = Mid(s2, j, 1) Then
Loop
If Then Label1.Caption = "是子集" Else Label1.Caption = "不是子集"
上述程序填空处的可选语句为:
①i = i + 1 ②j = j + 1 ③i > Len(s1) ④j > Len(s2)
则(1)(2)(3)处语句依次最合理的搭配为( )