LINQ到对象 [英] LINQ TO OBJECT

问题描述

T[] arr = ...;
var subsets = from m in Enumerable.Range(0, 1<< arr.Length)
              select
                  from i in Enumerable.Range(0, arr.Length)
                  where (m & (1 << i)) != 0
                  select arr[i];

谁能向我解释上面写的linq查询.
请说明流程的进行方式.

Can anyone explain to me the linq query written above.
Please explain how the flow will go.

推荐答案

似乎将所有子集(而不是所有排列)都移出了数组.
因此，如果该数组是包含"A"，"B"和"C"的字符串数组，它将返回四个子集:
"
"A"
"B"，
"A"，"B"

它通过创建一个外部索引数组来完成此操作，该数组包含从0到arr.Length - 1的所有索引(因此在上面的示例中为0、1、2、3.
然后，对于每个索引项，它将从数组中选择一项，其中内部索引(由Enumerable.Range(0, arr.Length)创建)是外部索引掩码的一部分.
例如，如果外部索引为3，则选择索引1和2.

(注意，我实际上没有运行代码，所以我可能会弄错了.)

希望这会有所帮助，
弗雷德里克(Fredrik)

It looks like it''s getting all the subsets (not all the permutations) out of the array.
So if the array is a string array containing "A", "B" and "C", it''s going to return four subsets:
""
"A"
"B",
"A", "B"

It does this by creating an outer index array containing all the indices from 0 to arr.Length - 1 (so in the above example that''s 0, 1, 2, 3.
Then, for each of those it will select the item from the array where the inner index (as created by Enumerable.Range(0, arr.Length)) is part of the outer index mask.
For example, if the outer index is 3 then index 1 and two are selected.

(Caveat, I haven''t actually run the code so I might be mistaken).

Hope this helps,
Fredrik

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