82 lines
2.4 KiB
VB.net
82 lines
2.4 KiB
VB.net
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Imports Microsoft.VisualBasic.Language.Python
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Namespace ComponentModel.Algorithm.DynamicProgramming
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''' <summary>
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''' Longest Common Subsequence
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''' </summary>
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Public Class LongestCommonSubsequence(Of T)
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Public Property length As Integer
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Public Property si As Integer
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Public Property ti As Integer
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Public Property reversed As Boolean
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Dim a As T()
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Dim b As T()
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Public ReadOnly Property Sequence() As T()
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Get
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If length >= 0 Then
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Return a.slice(si, si + length)
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Else
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Return {}
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End If
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End Get
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End Property
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Sub New(s As T(), t As T(), equals As IEquals(Of T))
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Dim mf = findMatch(s, t, equals)
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Dim tr = t.slice(0).Reverse().ToArray
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Dim mr = findMatch(s, tr, equals)
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If (mf(0) >= mr(0)) Then
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length = mf(0)
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si = mf(1)
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ti = mf(2)
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reversed = False
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Else
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length = mr(0)
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si = mr(1)
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ti = t.Length - mr(2) - mr(0)
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reversed = True
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End If
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End Sub
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''' <summary>
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'''
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''' </summary>
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''' <param name="s"></param>
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''' <param name="t"></param>
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''' <param name="equals"></param>
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''' <returns>``{length, si, ti}``</returns>
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Private Shared Function findMatch(s As T(), t As T(), equals As IEquals(Of T)) As Integer()
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Dim m = s.Length
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Dim n = t.Length
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Dim match = {0, -1, -1}
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Dim l = New Integer(m - 1)() {}
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For i As Integer = 0 To m - 1
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l(i) = New Integer(n - 1) {}
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For j As Integer = 0 To n - 1
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If equals(s(i), t(j)) Then
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Dim v = If(i = 0 OrElse j = 0, 1, l(i - 1)(j - 1) + 1)
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l(i)(j) = v
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If (v > match.Length) Then
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match(0) = v
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match(1) = i - v + 1
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match(2) = j - v + 1
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End If
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Else
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l(i)(j) = 0
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End If
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Next
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Next
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Return match
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End Function
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End Class
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End Namespace
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