在100个小球中,只有一个小球轻于其它小球。如何用没有砝码的天平找出该小球？小安设计了一个三分查找程序来快速查找这个小球，程序认定当需查找的小球个数小于3个时，认为已找到，程序运行界面如图。

Dim a(1 To 100) As Integer

Private Sub Form_Load()

    '产生100个重量为10的小球，存储在数组a中

    '其中随机选取1个小球的重量改为8，代码略

End Sub

Private Sub Command1_Click()

    Dim left As Integer, right As Integer

    Dim mid As Integer, count As Integer

    Dim s(1 To 2) As Integer

    left = 1: right = 100: count = 1

    List2.AddItem Str(left) + "-------->" + Str(right)

    Do While  left<=right

        s(1) = 0: s(2) = 0

            ①   

        i = left: k = 1

        Do While i <= left + mid * 2 - 1

            s(k) = s(k) + a(i)

            If     ②   Then k = k + 1

            i = i + 1

        Loop

        If s(1) = s(2) Then

            left = left + 2 * mid

        ElseIf s(1) < s(2) Then

            right = left + mid - 1

        Else

            

            left = left + mid

        End If

        count = count + 1

        List2.AddItem Str(left) + "-------->" + Str(right)

    Loop

    List2.AddItem "经过" + Str(count) + "次后找到这个数"

End Sub