题型：综合题 题类：模拟题 难易度：困难
浙江省五校2021届高三下学期信息技术5月联考试卷
现有VB程序用于判断某图能否一笔画成，若能，则通过穷举边的顺序来找到一种合法的路径。如c图有三条边，第1条由①②相连，第2条由④③相连，第3条由③②相连，若边的顺序231就是其中一种合法的边的顺序，代表先描第2条边，再描第3边，最后描第1条边，对应的路径④→③→②→①。在程序运行过程中，在文本框Text1中输入点的个数n，表示图中有n个点编号为1～n。在文本框Text2中输入若干点的编号，每两个点代表一条边(保证输入为偶数个点)，以“，”开头，点击“一笔画”按钮Command1后，在Label3中输出结果，在若能一笔画成，则输出一条路径，否则，提示“无法一笔画！”。程序界面如c图：
c图
Dim n As Integer, t As Integer, m As Integer, I As Integer, j As Integer
Dim ans As Integer, u As Integer, st As Integer, p As Long
Dim a(21) As Integer, b(11) As Integer, f(11) As Integer
Dim c(11)As Integer '用于存储构成一笔画各边的序号
Dim s As String, ss As String
Private Sub Command1_Click()
n= Val(Text1.Text)
s= Text2.Text: t= 0
For j= 1 To Len(s)
ch = Mid(s, j, 1)
If ch = "," Then
b(a(t)) = b(a(t)+1
t=t+1
a(t)= 0
Else
a(t)= a(t)*10 + Val(ch)
End If
Next j
: m=t\2: ans=0
st= 1
For i= 1 To n
If b(i) Mod 2=1 Then ans = ans+ 1: st=i
Next i
If ans=0 Or ans=2 Then
For p=1 To m^m '穷举边的顺序
If try(p) Then
u= st: ss = Str(u)
For j=1 To m
If (a(c(j)* 2)<>u) And (a(c(j)*2-1)<>u) Then Exit For
If Then u= a(c(j)*2- 1) Else u=a(c(j)*2)
ss=ss +"->"+ Str(u)
Next j
If j> m Then Exit For
End If
Next p
Else
ss="无法一笔画!"
End If
Label3.Caption=ss
End Sub
Function try(x As Long) As Boolean '生成边的访问顺序，并判断有无重复的边
Dim k As Integer, y As Long
y=x
For k=1 To m
c(k)=y Mod m+1: y-y\m
If f(c(k)) = x Then Exit For
Next k
If k> m Then try=True Else try = False
End Function
试题篮
'①
Then '②