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data.table vs dplyr: can one do something well the other can't or does poorly?
... remember is for it to return a list so that each element of the list gets converted to a column.
In dplyr, cannot do that. Have to resort to do() depending on how sure you are as to whether your function would always return a single value. And it is quite slow.
Once again, data.table's synta...
How to determine if a number is a prime with regex?
... String s which consists of repeating String t, finds t.
System.out.println(
"MamamiaMamamiaMamamia".replaceAll("^(.*)\\1+$", "$1")
); // prints "Mamamia"
The way it works is that the regex captures (.*) into \1, and then sees if there's \1+ following it. Using the ^ and $ ensures...
Maximum number of characters using keystrokes A, Ctrl+A, Ctrl+C and Ctrl+V
This is an interview question from google. I am not able to solve it by myself. Can somebody shed some light?
14 Answers
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ZeroMQ的学习和研究（PHP代码实例） - C/C++ - 清泛网 - 专注C/C++及内核技术
...
// Wait for next request from client
$request = $responder->recv ();
printf ("Received request: [%s]\n", $request);
// Do some 'work'
sleep (1);
// Send reply back to client
$responder->send ("World");
}
Client 程序如下：
<?php
/*
* Hello World client
* Connec...
How does database indexing work? [closed]
...in much the same way as linked lists; both contain a section for data, a pointer to the location of the next node (or block), and both need not be stored contiguously.
Due to the fact that a number of records can only be sorted on one field, we can state that searching on a field that isn’t sorte...
How much of a git sha is *generally* considered necessary to uniquely identify a change in a given c
... Note also, though, that this of course only applies for the moment Git prints the SHA. If you "save" abbreviated SHAs (say, in logs, emails, IMs, etc.) and use them later to refer to commits, they might no longer be unique! While certainly unlikely for normal lengths like 7-12 characters, if you d...
ZMQ: 基本原理 - 开源 & Github - 清泛网 - 专注C++内核技术
...文件描述符）去定位具体的拓扑： /* Topology establishment */int s = zmq_socket (...);zmq_connect (s, "tcp://192.168.0.111:5555");/* Message routing */const char data [] = "ABC";zmq_send (s, data, sizeof (data), 0); 区分拓扑建立和消息路由严格地说不是不可缺少的。...
If Python is interpreted, what are .pyc files?
I've been given to understand that Python is an interpreted language...
However, when I look at my Python source code I see .pyc files, which Windows identifies as "Compiled Python Files".
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Optimizing away a “while(1);” in C++0x
...ll and the document refers to both WG14 and WG21:
As N1509 correctly points out, the current draft essentially gives
undefined behavior to infinite loops in 6.8.5p6. A major issue for
doing so is that it allows code to move across a potentially
non-terminating loop. For example, assume we ...
Is 'switch' faster than 'if'?
...ler worth its salt is going to see an if / else if ladder and transform it into equivalent switch or vice versa if it would be faster to do so.
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