關鍵字.NET

Question

我需要計算每個關鍵字多少次重複發生在一個字符串，通過次數最多的排序。 用於此目的的.NET代碼中可用的最快算法是什麼？

Answer 1

編輯：下面的代碼組，計

string[] target = src.Split(new char[] { ' ' }); 

var results = target.GroupBy(t => new 
{ 
    str = t, 
    count = target.Count(sub => sub.Equals(t)) 
}); 

這終於開始讓我更有意義的獨特記號......

編輯：下面的子目標相關的計數結果代碼：

string src = "for each character in the string, take the rest of the " + 
    "string starting from that character " + 
    "as a substring; count it if it starts with the target string"; 
string[] target = {"string", "the", "in"}; 

var results = target.Select((t, index) => new {str = t, 
    count = src.Select((c, i) => src.Substring(i)). 
    Count(sub => sub.StartsWith(t))}); 

結果現在是：

+  [0] { str = "string", count = 4 } <Anonymous Type> 
+  [1] { str = "the", count = 4 } <Anonymous Type> 
+  [2] { str = "in", count = 6 } <Anonymous Type> 

下面

原始代碼：

string src = "for each character in the string, take the rest of the " + 
    "string starting from that character " + 
    "as a substring; count it if it starts with the target string"; 
string[] target = {"string", "the", "in"}; 

var results = target.Select(t => src.Select((c, i) => src.Substring(i)). 
    Count(sub => sub.StartsWith(t))).OrderByDescending(t => t); 

與感激確認給this previous response。從調試

結果（這需要額外的邏輯包括匹配的字符串，其計數）：

-  results {System.Linq.OrderedEnumerable<int,int>}  
-  Results View Expanding the Results View will enumerate the IEnumerable 
     [0] 6 int 
     [1] 4 int 
     [2] 4 int 

Answer 2

您可以將字符串分解爲一個字符串集合，每個字符一個字符串，然後對該集合執行LINQ查詢。雖然我懷疑它會是最快的，但它可能比正則表達式更快。

Answer 3

說不上大約最快的，但LINQ的可能是最理解：

var myListOfKeywords = new [] {"struct", "public", ...}; 

var keywordCount = from keyword in myProgramText.Split(new []{" ","(", ...}) 
    group by keyword into g 
    where myListOfKeywords.Contains(g.Key) 
    select new {g.Key, g.Count()} 

foreach(var element in keywordCount) 
    Console.WriteLine(String.Format("Keyword: {0}, Count: {1}", element.Key, element.Count)); 

您可以在非LINQ的-Y方式寫這篇文章，但基本前提是相同的;將字符串分成單詞，並計算每個感興趣單詞的出現次數。

Answer 4

簡單算法：將字符串拆分爲單詞數組，迭代該數組，並將每個單詞的計數存儲在散列表中。完成後按計數排序。