大约有 531 项符合查询结果（耗时：0.0140秒） [XML]
Why does C++ require a user-provided default constructor to default-construct a const object?
...type X (or array thereof), X
is const-default-constructible,
if T is a union with at least one non-static data member, exactly one variant member has a default member initializer,
if T is not a union, for each anonymous union member with at least one non-static data member (if any), exactly on...
What guarantees are there on the run-time complexity (Big-O) of LINQ methods?
...).
Distinct, GroupBy Join, and I believe also the set-aggregation methods (Union, Intersect and Except) use hashing, so they should be close to O(N) instead of O(N²).
Contains checks for an ICollection implementation, so it may be O(1) if the underlying collection is also O(1), such as a HashSet<...
Difference between CTE and SubQuery?
... most useful for recursion:
WITH hier(cnt) AS (
SELECT 1
UNION ALL
SELECT cnt + 1
FROM hier
WHERE cnt < @n
)
SELECT cnt
FROM hier
will return @n rows (up to 101). Useful for calendars, dummy rowsets etc.
They are also more readable (i...
How to declare a type as nullable in TypeScript?
...wever, salary = undefined; will work just fine in this case. Solution: use Union i.e. '|'
– Ankur Nigam
Apr 21 at 6:19
...
How to delete duplicate rows in SQL Server?
...n (
select min(id) from search
group by url
having count(*)=1
union
SELECT min(id) FROM search
group by url
having count(*) > 1
)
share
|
improve this answer
|
...
Split function equivalent in T-SQL?
...1,12,13,14,15'
SET @delimiter = ','
;WITH cte AS
(
SELECT 0 a, 1 b
UNION ALL
SELECT b, CHARINDEX(@delimiter, @str, b) + LEN(@delimiter)
FROM CTE
WHERE b > a
)
SELECT SUBSTRING(@str, a,
CASE WHEN b > LEN(@delimiter)
THEN b - a - LEN(@delimiter)
ELSE LEN(@str) - a +...
how to concatenate two dictionaries to create a new one in Python? [duplicate]
...ems() for d in (d1, d2, d3)))
and:
from itertools import chain
def dict_union(*args):
return dict(chain.from_iterable(d.items() for d in args))
Python 2.6 & 2.7
from itertools import chain
dict(chain.from_iterable(d.iteritems() for d in (d1, d2, d3))
Output:
>>> from iterto...
What is the most efficient/elegant way to parse a flat table into a tree?
...RECURSIVE MyTree AS (
SELECT * FROM MyTable WHERE ParentId IS NULL
UNION ALL
SELECT m.* FROM MyTABLE AS m JOIN MyTree AS t ON m.ParentId = t.Id
)
SELECT * FROM MyTree;
I tested recursive queries in MySQL 8.0 in my presentation Recursive Query Throwdown in 2017.
Below is my original an...
How to replace (or strip) an extension from a filename in Python?
...pping it all up in a function
from pathlib import Path
from typing import Union
PathLike = Union[str, Path]
def replace_ext(path: PathLike, new_ext: str = "") -> Path:
extensions = "".join(Path(path).suffixes)
return Path(str(p).replace(extensions, new_ext))
p = Path("/path/to/myfil...
When should I use Kruskal as opposed to Prim (and vice versa)?
...c.
If you implement both Kruskal and Prim, in their optimal form : with a union find and a finbonacci heap respectively, then you will note how Kruskal is easy to implement compared to Prim.
Prim is harder with a fibonacci heap mainly because you have to maintain a book-keeping table to record the...