-1+2-3+4-...n ,n从键盘上输入,求和S(使用循环结构解决此问题)这是一道VB的题，求大神帮解决.流程图+代码

Question

如题所述

Answer 1

Private Sub Command1_Click()
Dim N As Integer
Dim i As Integer
Dim SUM As Integer
Dim Symbol As Integer
Symbol = -1
N = Val(InputBox("请输入n"))
For i = 1 To N
SUM = SUM + i * Symbol
Symbol = Symbol * (-1)
Next i
Form1.Print "当N="; N, "结果是：", SUM
End Sub

在窗体上建一个按钮，然后在代码框里输入以上代码。

Answer 2

for i=1 to n
if n mod 2 =0 then‘ 如果能被2整除，说明是偶数，就加上
s=s+i
else’ 不能被2整除，说明是基数，就减掉
s=s-i
end if
next i

Answer 3

Private Sub Command1_Click()
On Error GoTo out '当发生错误
Dim Inputnum As Long
Dim Sum As Long
Inputnum = InputBox("请输入n的值", "输入")
Form1.Cls
Print "当n值为" & Inputnum&; "时:"
For i = 1 To Inputnum
a = i Mod 2
If a = 1 Then
Sum = Sum + i * -1
ElseIf a = 0 Then
Sum = Sum + i
End If
Next i
Print "输出结果：" & Sum '输出结果
Exit Sub '退出过程
out:
MsgBox "未知错误：溢出", , "请重新输入"
End Sub