[英]Divide list in sublists by elements
我有一個字符串列表:
{"foo", "str1", "str2", ..., "bar", ..., "baz", ...}
我需要在"foo"
, "bar"
和"baz"
之間獲得字符串的子列表。
用linq可以做到這一點嗎?
編輯
我需要一個方法,而不是兩次查看列表。
您可以這樣做來細化任何兩個其他元素之間的所有元素:
var strings = new[] { "foo", "str1", "str2", ... "bar", ... "baz" };
var between = strings.SkipWhile(s => s != "foo").Skip(1)
.TakeWhile(s => s != "bar"); // "str1", "str2", ...
如果你想獲得“foo”和“baz”之間的所有內容,除了“bar”,請使用此(假設訂單為“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,如果您習慣使用具有副作用的Linq查詢,則可以通過某些“停止”單詞對輸入列表進行分區:
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" }
或稍高效(因為它在第三個停用詞之后停止處理):
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" }
現在,這個方法在邊緣有點粗糙,當它涉及“foo”之前或“baz”之后的項目時有點繁瑣,但是如果因為你只是在尋找“foo”和“baz”之間的項目,它應該適合你。 它具有額外的好處,即停用詞的順序不會影響結果。
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);
如果您只想通過擴展數據列表迭代一次,則可以執行以下操作:
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);
});
至少使用一點linq,但只需通過您的大量數據列表迭代一次。
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