Question

我一直试图在最后一小时解决这个问题，我几乎让它起作用，但它只显示了未反转的字样。我不知道为什么会这样。我知道这是一个初学者问题，但请帮忙。感谢。

Private Sub btnReverse_Click(sender As Object, e As EventArgs) Handles btnReverse.Click

    Dim strInput As String
    Dim strLetter As String
    Dim intLength As Integer

    strInput = txtWord.Text
    intLength = strInput.Length
    '!!de-incremented because index starts at 0!!
    intLength = intLength - 1

    Dim indexReverse As Integer = intLength

    For index As Integer = 0 To intLength Step +1
        'get letter at this index
        strLetter = strInput.Substring(index, 1)
        'remove letter just got
        strInput = strInput.Remove(index, 1)
        'insert new letter at old letter place
        strInput = strInput.Insert(indexReverse, strLetter)

        indexReverse = indexReverse - 1
    Next

    lblReverse.Text = strInput

End Sub

好的，所以我根据kjtl的想法编辑了我的代码，现在我得到一个参数输出范围。我知道这意味着什么，但我不明白为什么我得到这个例外。重申一下，我想尽可能少地编辑此代码以使其工作。这两种想法都是更简单的方法，我只是想修复我的代码，而不是为教育目的而全部替换它。

Private Sub btnReverse_Click(sender As Object, e As EventArgs) Handles btnReverse.Click

    Dim strInput As String
    Dim strOutput As String = ""
    Dim strLetter As String
    Dim intLength As Integer
    Dim chrPadding As Char = Convert.ToChar(" ")

    strInput = txtWord.Text
    intLength = strInput.Length
    '!!de-incremented because index starts at 0!!
    intLength = intLength - 1

    Dim indexReverse As Integer = intLength

    For index As Integer = 0 To intLength Step +1
        'get letter at this index
        strLetter = strInput.Substring(index, 1)
        'assign temp values to strOutput
        strOutput = strOutput.PadRight(intLength, chrPadding)
        'remove letter just got
        strOutput = strOutput.Remove(index, 1)
        'insert new letter at old letter place
        strOutput = strOutput.Insert(indexReverse, strLetter)

        indexReverse = indexReverse - 1
    Next

    lblReverse.Text = strInput

End Sub

Answer 1

Array类有Reverse方法

反转整个一维数组中元素的序列

现在，字符串类有一个方法可以将字符串的单个char元素提取为字符数组。此时解决方案非常简单。

Dim strInput = "This is a Test"
Dim c = test.ToCharArray()
Array.Reverse(c)
Dim reversed = new String(c)
Console.WriteLine(reversed)

或者如果您喜欢单线解决方案

Dim strInput = "This is a Test"
Dim reversed = new String(strInput.ToCharArray().Reverse().ToArray())

Answer 2

您可以使用StrReverse：

Dim str As String = "hello"
Dim strRev As String = StrReverse(str) 'olleh

或者这个（如果你更愿意避免使用VisualBasic命名空间）：

Dim strRev2 As New String(str.Reverse.ToArray) 'olleh

另见：

Best way to reverse a string @ StackOverflow

向后显示一个单词vb

2 个答案: