Question

Public Sub BinarySearch_Surname(ByVal BrownieArray() As Brownie_Structure, ByVal SearchItem As String, ByVal LowInt As Integer, ByVal HighInt As Integer)
    Dim ItemFound As Boolean = False
    Dim SearchFailed As Boolean = False
    Dim Midpoint As Integer = Int((LowInt + HighInt) / 2)

    Try
        If BrownieArray(Midpoint).Surname = SearchItem Then
            ItemFound = True
        Else
            If LowInt >= HighInt Then
                SearchFailed = True
            Else
                If BrownieArray(Midpoint).Surname < SearchItem Then
                    **BinarySearch_Surname(BrownieArray, Midpoint + 1, HighInt, ItemFound)
                Else
                    BinarySearch_Surname(BrownieArray, LowInt, Midpoint - 1, HighInt)**
                End If
            End If
        End If
        If SearchFailed = True Then
            MessageBox.Show("Failed to find Suranme in database", "Error Message", MessageBoxButtons.OK, MessageBoxIcon.Error)
            Exit Sub
        End If
        If ItemFound = True Then
            MessageBox.Show("Surname: " & BrownieArray(Midpoint).Surname, "Found", MessageBoxButtons.OK, MessageBoxIcon.Information)
            Exit Sub
        End If
    Catch
        MessageBox.Show("Failed to find , please insert correct infomation and try again", "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning)
        Exit Sub
    End Try
End Sub

使用这种递归算法发生StackOverflow，我知道为什么会导致错误，但不知道如何解决它？

Answer 1

这一行：

If LowInt >= HighInt Then

应该是：

If LowInt > HighInt Then

这一行：

BinarySearch_Surname(BrownieArray, Midpoint + 1, HighInt, ItemFound)

应该是：

BinarySearch_Surname(BrownieArray, SearchItem, Midpoint + 1, HighInt)

这一行：

BinarySearch_Surname(BrownieArray, LowInt, Midpoint - 1, HighInt)

应该是：

BinarySearch_Surname(BrownieArray, SearchItem, LowInt, Midpoint - 1)

Answer 2

您将错误的参数传递给递归调用，它应该是这样的：

  If BrownieArray(Midpoint).Surname < SearchItem Then
      BinarySearch_Surname(BrownieArray, SearchItem, Midpoint + 1, HighInt)
  Else
      BinarySearch_Surname(BrownieArray, SearchItem, LowInt, Midpoint - 1)                
  End If

你的递归退出条件也是错误的，它应该是：

  If LowInt > HighInt Then // > instead of >=

此外，您可以将SUB转换为返回值的函数，以便将这些消息框保留在搜索代码之外。

在VB 2010中使用BinarySearch的Stackoverflow问题

2 个答案: