Question

我已经编写了这个函数，用于从字符串数组中的不同值自动将性别更正为M或F.它工作正常但我的经理告诉我使用Dictionary，他说效率更高。但我不知道。有谁想帮我理解如何做到这一点？感谢。

    Public Function AutoGender(ByVal dt As DataTable) As DataTable        

    Dim Gender As String = ""
    Dim Mkeywords() As String = {"boy", "boys", "male", "man", "m", "men", "guy"}
    Dim Fkeywords() As String = {"girl", "girls", "female", "woman", "f", "women", "chick"}
    Dim row As DataRow
        For Each row In dt.Rows
            If Mkeywords.Contains(row("Gender").ToString.ToLower) Then
                Gender = "M"
                row("Gender") = Gender
            ElseIf Fkeywords.Contains(row("Gender").ToString.ToLower) Then
                Gender = "F"
                row("Gender") = Gender
            End If
        Next
    Return dt

    End Function

Answer 1

以下示例说明如何实现Dictionary(Of String, String)以查找此同义词是否已知：

Shared GenderSynonyms As Dictionary(Of String, String) = New Dictionary(Of String, String) From
    {{"boy", "M"}, {"boys", "M"}, {"male", "M"}, {"man", "M"}, {"m", "M"}, {"men", "M"}, {"guy", "M"},
     {"girl", "F"}, {"girls", "F"}, {"female", "F"}, {"woman", "F"}, {"f", "F"}, {"women", "F"}, {"chick", "F"}}

Public Function AutoGender(ByVal dt As DataTable) As DataTable
    If dt.Columns.Contains("Gender") Then
        For Each row As DataRow In dt.Rows
            Dim oldGender = row.Field(Of String)("Gender").ToLower
            Dim newGender As String = String.Empty
            If GenderSynonyms.TryGetValue(oldGender, newGender) Then
                row.SetField("Gender", newGender)
            End If
        Next
    End If
    Return dt
End Function

请注意，我已使用collection initializer填充Dictionary，这是使用文字初始化集合的便捷方式。您也可以使用Add method。

修改：另一种可能更简洁的方法是使用两个HashSet(Of String)，一个用于男性同义词，另一个用于女性：

Shared maleSynonyms As New HashSet(Of String) From
    {"boy", "boys", "male", "man", "m", "men", "guy"}
Shared femaleSynonyms As New HashSet(Of String) From
    {"girl", "girls", "female", "woman", "f", "women", "chick"}

Public Function AutoGender(ByVal dt As DataTable) As DataTable
    If dt.Columns.Contains("Gender") Then
        For Each row As DataRow In dt.Rows
            Dim oldGender = row.Field(Of String)("Gender").ToLower
            Dim newGender As String = String.Empty
            If maleSynonyms.Contains(oldGender) Then
                row.SetField("Gender", "M")
            ElseIf femaleSynonyms.Contains(oldGender) Then
                row.SetField("Gender", "F")
            End If
        Next
    End If
    Return dt
End Function

HashSet也必须是唯一的，因此它不能包含重复的Strings（如Dictionary中的密钥），但它不是键值对，而只是一组。

Answer 2

只需将两个数组更改为字典，然后执行ContainsKey而不是Contains。

Dim Mkeywords = New Dictionary(Of String, String) From
    {{"boy", ""}, {"boys", ""}, {"male", ""}, {"man", ""}, {"m", ""}, {"men", ""}, {"guy", ""}}

（并为女性效仿）

然而，正如你可能已经注意到我把所有那些空字符串放进去了。这是因为字典具有值和键，但由于我们不使用这些值，因此我将它们设为空字符串。要获得相同的O(1)查找但避免所有无关的值，您可以以类似的方式使用HashSet。

现在你需要改变的就是，就像我说的那样，使用ContainsKey（或HashSet，如果你走这条路，它还只是Contains）：< / p>

If Mkeywords.ContainsKey(row("Gender").ToString.ToLower) Then

最后一点说明：这只会更高效，而且效率更高。如果数据开始大幅增长。就像你拥有它一样，只有那么少的元素，使用字典甚至可能会更慢。

如何在VB.net中使用Dictionary？

2 个答案: