VB 用自定义函数(function)，求1！+2！+3！+…+10！并用print显示结果?

Question

一定要在VB里求:

用自定义函数(function)，求1！+2！+3！+…+10！并用print显示结果?
Private Sub Command1_click()

End Sub
function fact(x as integer) as long

end function

Answer 1

Private Sub Command1_click()
dim i as integer
dim sum as long
for i=1 to 10
sum=sum+fact(i)
next
debug.print sum
End Sub

function fact(x as integer) as long
if x=1 then
fact=1
else
fact=x*fact(x-1)
end if
end function

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虽然这样写结构清晰，但运算量大，算阶乘的时候一共要乘45次

完全可以改成
Private Sub Command1_click()
dim i as integer
dim jie as long
dim sum as long
jie=1
for i=1 to 10
jie=jie*i
sum=sum+jie
next
debug.print sum
End Sub

这样算所有阶乘一共只需要乘10次

ps: 乘法要比加法浪费多的多的CPU时间

Answer 2

找一个现成的

Private Sub Command1_Click()
n = InputBox("输入自然数", "输入")
JieCheng n
If n > 1 Then
For j = n To 2 Step -1
Print j & "*";
Next j
End If
Print "1=";
Print JieCheng(n)
End Sub

Private Function JieCheng(ByVal i&) As Long
If i > 1 Then
JieCheng = i * JieCheng(i - 1)
Else
JieCheng = 1
End If
End Function

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