Question

我正在使用程序，请参阅此处：Visual Basic Regular Expression Question。我输入字母，程序从列表中返回所有可能的组合。我想改变这行代码...

Dim result = fruits.Where(Function(fruit) Not fruit.Except(letters).Any())

如果我有这个清单：

 Dim fruit as List(Of string) from {"apple","orange","pear","banana"}

我输入“p a p l e r”然后它将返回“apple”和“pear”，但是如果我输入“a p l e r”那么它将返回“pear”。我们的想法是返回所有单词，这些单词可以由输入的字母组成，而不会复制任何单个字母。如何优化这个Linq代码？

Answer 1

这可能更干净，但有效：

Dim fruits As New List(Of String) From { "apple", "orange", "pear", "banana" }
Dim input As String = "a,p,l,e,r"
dim inputLetters = from letter in input.Replace(",", "") group by letter into Group select group.first, Group.Count

dim result = fruits.where(
    function(fruit) 
        dim fruitcounts = from letter in fruit group by letter into Group select group.first,  group.count 
        dim res = from fc in fruitcounts, inputs in inputletters where fc.first = inputs.first andalso fc.count <= inputs.count select fc.first
        return res.count = fruit.count
    end function
    )

编辑 - 我删除了一些不需要的订单，并简化了分组

再次编辑 - 经过一番思考之后，这里有一个版本，它有更多的行，但是更清晰，更好的因素：

Sub Main

    Dim fruits As New List(Of String) From { "apple", "orange", "pear", "banana" }
    Dim input As String = "a,p,l,e,r"

    dim matchingFruits = from fruit in fruits where CanBeMadeFrom(fruit, input)

End Sub

Function StringToFrequencyTable(input as string) as Dictionary(of Char, Integer)

    dim freqTable = from letter in input 
                    group by letter into Group
                    select letter, Group.Count()

    return freqTable.ToDictionary(function(g) g.Letter, function(g) g.Count)

end function

Function CanBeMadeFrom(candidate as string, letters as string) as boolean

    dim inputLetters = StringToFrequencyTable(letters.replace(",", ""))
    dim IsCharInFrequencyTable = function(x) (from entry in inputLetters where entry.Key = x.Key andalso entry.Value >= x.Value).Any()

    return StringToFrequencyTable(candidate).All( IsCharInFrequencyTable )

end function

如果我对此做了其他任何事情，我会将CanBeMadeFrom和StringToFrequencyTable变为扩展方法。

Linq从列表中获取单词

1 个答案: