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C#中利用HashSet代替List - 更多技术 - 清泛网 - 专注C/C++及内核技术
C#中利用HashSet代替ListC#需要存储一个集合，然后判断集合是否已包含某元素等等。我相信大部分人会选择使用List，当然没有问题，但是若集合数据量很大，这时就要考虑性能问题了，HashSet刚好派上用场，而且性能提升不只一点...
Comparing two dictionaries and checking how many (key, value) pairs are equal
... will fail on values that aren't hashable.
– Tim Tisdall
Apr 10 '17 at 13:51
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show 3 more comments
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Can dplyr package be used for conditional mutating?
...and the conditions (except for the default value of NA at the end) are mutually exclusive, as is the case in the question, then we can use an arithmetic expression such that each term is multiplied by the desired result using na_if at the end to replace 0 with NA.
df %>%
mutate(g = 2 * (a == 2 ...
The difference between Classes, Objects, and Instances
...he set of values that is the type Y.
So that's what the term "instance" really means: it describes a relationship not a thing.
The type system of the Java programming language supports two kinds of types, primitive types and reference types. The reference types are further divided into the classe...
How to dump a table to console?
I'm having trouble displaying the contents of a table which contains nested tables (n-deep). I'd like to just dump it to std out or the console via a print statement or something quick and dirty but I can't figure out how. I'm looking for the rough equivalent that I'd get when printing an NSDicti...
How to get the last N rows of a pandas DataFrame?
...000/svg\"\u003e\u003cpath d=\"M46.1709 9.17788C46.1709 8.26454 46.2665 7.94324 47.1084 7.58816C47.4091 7.46349 47.7169 7.36433 48.0099 7.26993C48.9099 6.97997 49.672 6.73443 49.672 5.93063C49.672 5.22043 48.9832 4.61182 48.1414 4.61182C47.4335 4.61182 46.7256 4.91628 46.0943 5.50789C45.7307 4.9328 4...
Hibernate Annotations - Which is better, field or property access?
...d to add logic for", or "xxxx breaks encapsulation". However, nobody has really commented on the theory, and given a properly reasoned argument.
What is Hibernate/JPA actually doing when it persists an object - well, it is persisting the STATE of the object. That means storing it in a way that it ...
Git Clone: Just the files, please?
...hive.
See backing up project which uses git: it will include in an archive all files (including submodules if you are using the git-archive-all script)
You can then use that archive anywhere, giving you back only files, no .git directory.
git archive --remote=<repository URL> | tar -t
If y...
fork() branches more than expected?
...000/svg\"\u003e\u003cpath d=\"M46.1709 9.17788C46.1709 8.26454 46.2665 7.94324 47.1084 7.58816C47.4091 7.46349 47.7169 7.36433 48.0099 7.26993C48.9099 6.97997 49.672 6.73443 49.672 5.93063C49.672 5.22043 48.9832 4.61182 48.1414 4.61182C47.4335 4.61182 46.7256 4.91628 46.0943 5.50789C45.7307 4.9328 4...
Multiple GitHub Accounts & SSH Config
...es to the Host * section of your ~/.ssh/config file. This tells ssh to actually use the IdentityFiles you specify, rather than spamming the server with all of them.
– Mechanical snail
May 9 '12 at 7:18
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