按元素划分子列表中的列表

本文关键字：列表 元素 划分 | 更新日期: 2023-09-27 18:17:57

我有一个字符串列表:

{"foo", "str1", "str2", ..., "bar", ..., "baz", ...}

我需要得到"foo", "bar"和"baz"之间字符串的子列表。

可以用linq来做这个吗?

编辑

按元素划分子列表中的列表

您可以这样做来区分任意两个元素之间的所有元素:

var strings = new[] { "foo", "str1", "str2", ... "bar", ... "baz" };
var between = strings.SkipWhile(s => s != "foo").Skip(1)
                     .TakeWhile(s => s != "bar"); // "str1", "str2", ...

如果你想获得"foo"answers"baz"之间的所有内容，除了"bar"，使用这个(假设顺序为"foo"， "bar"， "baz"):

var strings = new[] { "foo", "str1", "str2", ... "bar", ... "baz" };
var between = strings.SkipWhile(s => s != "foo").Skip(1)
                     .TakeWhile(s => s != "baz")
                     .Where(s => s != "bar"); // "str1", "str2", ...

或者如果你愿意使用有副作用的Linq查询，你可以这样做，通过某些'stop'词来划分你的输入列表:

 var stops = new[] { "foo", "bar", "baz" };
 var strings = new[] { "foo", "str1", "str2", "bar", "str3", "baz" };
 var p = -1;
 var partitions = 
     from s in strings
     let i = Array.IndexOf(stops, s) 
     group s by p = i == -1 ? p : i into g
     where g.Key == 0 || g.Key == 1
     select g.Skip(1); // { "str1", "str2" }, { "str3" }

或者更有效率一点(因为它在第三个停止字之后停止处理):

 var partitions = 
     (from s in strings
      let i = Array.IndexOf(stops, s) 
      group s by p = i == -1 ? p : i)
     .SkipWhile(g => g.Key < 0)
     .Take(2)
     .Select(g => g.Skip(1)); // { "str1", "str2" }, { "str3" }

现在，这个方法有点粗糙，当涉及到"foo"之前或"baz"之后的项目时，它有点繁琐，但如果你只寻找"foo"answers"baz"之间的项目，它应该为你工作。它还有一个额外的好处，即停止词的顺序不会影响结果。

var idxFoo = list.IndexOf("foo");
var idxBar = list.IndexOf("bar");
var idxBaz = list.IndexOf("baz");
var subList1 = list.Skip(idxFoo).Take(idxBar - idxFoo);
var subList2 = list.Skip(idxBar).Take(idxBaz - idxBar);

如果你只想在你的扩展数据列表中迭代一次，你可以这样做:

List<string> longDataList = new List<string> { "foo", "str1", "str2", "str1", "str2", "str1", "str2", "bar", "str1", "str2", "str1", "str2", "str1", "str2", "baz", "str1", "str2", "str1", "str2", "str1", "str2" };
List<string> splitters = new List<string> { "foo", "bar", "baz" };
Dictionary<string, List<string>> resultDict = new Dictionary<string, List<string>>();
List<string> currentList = null;
longDataList.ForEach(s =>
    {
       if (splitters.Contains(s))
          {
            if (resultDict.ContainsKey(s))
                currentList = resultDict[s];
             else
                {
                 currentList = new List<string>();
                  resultDict.Add(s, currentList);
                }
           }
        else
           currentList.Add(s);
     });

至少使用了一点linq，但在您的扩展数据列表中只迭代一次。

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