VB.NET2005通过泛型实现的KMP查找算法

增强型的模式匹配算法，KMP查找算法VB.NET 2005泛型实现。也不知道用的对不对，但是个人感觉好像是对的。不过做测试的时候发现如果是字符串（字符数组）的匹配，用KMP算法比.NET自己的String.IndexOf还要慢。不知道.NET怎么做的，可能也是KMP算法吧。

和2003版的一样，主函数KMPSearch进行实际的匹配操作。子函数KMPSearchGetNextArray负责计算匹配串每个项目单位对应的权值。只不过加入了(Of T As IComparable(Of T))泛型约束。

    Public Shared Function KMPSearch(Of T As IComparable(Of T))(ByVal src() As T, ByVal key() As T) As Integer

        Dim ret As Integer = 0

        Dim arrNext() As Integer

        Dim inti As Integer = 1

        Dim intj As Integer = 1

        If src Is Nothing OrElse key Is Nothing OrElse key.Length > src.Length Then

            ret = -1

        Else

            arrNext = KMPSearchGetNextArray(Of T)(key)

            While inti <= src.Length AndAlso intj <= key.Length

                If intj = 0 OrElse src(inti - 1).Equals(key(intj - 1)) = True Then

                    inti = inti + 1

                    intj = intj + 1

                Else

                    intj = arrNext(intj)

                End If

            End While

            If intj > key.Length Then

                ret = inti - key.Length - 1

            Else

                ret = -1

            End If

        End If

        Return ret

    End Function

 

    Private Shared Function KMPSearchGetNextArray(Of T As IComparable(Of T))(ByVal key() As T) As Integer()

        Dim arrNext(key.Length) As Integer

        Dim intj As Integer = 1

        Dim intk As Integer = 0

        arrNext(1) = 0

        While intj < key.Length

            If intk = 0 OrElse key(intj - 1).Equals(key(intk - 1)) = True Then

                intj = intj + 1

                intk = intk + 1

                arrNext(intj) = intk

            Else

                intk = arrNext(intk)

            End If

        End While

        Return arrNext

    End Function