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1500 questions
4170
votes
38 answers
How can I pair socks from a pile efficiently?
Yesterday I was pairing the socks from the clean laundry and figured out the way I was doing it is not very efficient. I was doing a naive search — picking one sock and "iterating" the pile in order to find its pair. This requires iterating over n/2…
amit
- 175,853
- 27
- 231
- 333
4123
votes
13 answers
grep: show lines surrounding each match
How do I grep and show the preceding and following 5 lines surrounding each matched line?
Mark Harrison
- 297,451
- 125
- 333
- 465
4093
votes
42 answers
What is the !! (not not) operator in JavaScript?
I saw some code that seems to use an operator I don't recognize, in the form of two exclamation points, like so: !!. Can someone please tell me what this operator does?
The context in which I saw this was,
this.vertical = vertical !== undefined ?…
Hexagon Theory
- 43,627
- 5
- 26
- 30
4089
votes
73 answers
How can I validate an email address using a regular expression?
Over the years I have slowly developed a regular expression that validates most email addresses correctly, assuming they don't use an IP address as the server part.
I use it in several PHP programs, and it works most of the time. However, from time…
acrosman
- 12,814
- 10
- 39
- 55
4080
votes
33 answers
Is there a CSS parent selector?
How do I select the element that is a direct parent of the anchor element?
As an example, my CSS would be something like this:
li < a.active {
property: value;
}
Obviously there are ways of doing this with JavaScript, but I'm hoping that…
jcuenod
- 55,835
- 14
- 65
- 102
4073
votes
73 answers
How do I generate random integers within a specific range in Java?
How do I generate a random int value in a specific range?
The following methods have bugs related to integer overflow:
randomNum = minimum + (int)(Math.random() * maximum);
// Bug: `randomNum` can be bigger than `maximum`.
Random rn = new…
user42155
- 48,965
- 27
- 59
- 60
4073
votes
42 answers
Create ArrayList from array
Given an array of type Element[]:
Element[] array = {new Element(1), new Element(2), new Element(3)};
How do I convert this array into an object of type ArrayList?
ArrayList arrayList = ???;
Ron Tuffin
- 53,859
- 24
- 66
- 78
4063
votes
91 answers
How to round to at most 2 decimal places, if necessary
I'd like to round at most two decimal places, but only if necessary.
Input:
10
1.7777777
9.1
Output:
10
1.78
9.1
How can I do this in JavaScript?
stinkycheeseman
- 43,437
- 7
- 30
- 49
4048
votes
60 answers
Sort array of objects by string property value
I have an array of JavaScript objects:
var objs = [
{ first_nom: 'Lazslo', last_nom: 'Jamf' },
{ first_nom: 'Pig', last_nom: 'Bodine' },
{ first_nom: 'Pirate', last_nom: 'Prentice' }
];
How can I sort them by the value of…
Tyrone Slothrop
- 40,787
- 3
- 17
- 8
3997
votes
137 answers
Message 'src refspec master does not match any' when pushing commits in Git
I clone my repository with:
git clone ssh://xxxxx/xx.git
But after I change some files and add and commit them, I want to push them to the server:
git add xxx.php
git commit -m "TEST"
git push origin master
But the error I get back is:
error: src…
sinoohe
- 40,334
- 3
- 19
- 16
3990
votes
23 answers
Make an existing Git branch track a remote branch?
I know how to make a new branch that tracks remote branches, but how do I make an existing branch track a remote branch?
I know I can just edit the .git/config file, but it seems there should be an easier way.
Pat Notz
- 208,672
- 30
- 90
- 92
3990
votes
12 answers
Proper use cases for Android UserManager.isUserAGoat()?
I was looking at the new APIs introduced in Android 4.2.
While looking at the UserManager class I came across the following method:
public boolean isUserAGoat()
Used to determine whether the user making this call is subject to…
Ovidiu Latcu
- 71,607
- 15
- 76
- 84
3976
votes
33 answers
Checking if a key exists in a JavaScript object?
How do I check if a particular key exists in a JavaScript object or array?
If a key doesn't exist, and I try to access it, will it return false? Or throw an error?
Adam Ernst
- 52,440
- 18
- 59
- 71
3965
votes
46 answers
Loop through an array in JavaScript
In Java, you can use a for loop to traverse objects in an array as follows:
String[] myStringArray = {"Hello", "World"};
for (String s : myStringArray) {
// Do something
}
Can I do the same in JavaScript?
Mark Szymanski
- 56,590
- 24
- 70
- 87
3945
votes
33 answers
How to iterate over rows in a DataFrame in Pandas
I have a pandas dataframe, df:
c1 c2
0 10 100
1 11 110
2 12 120
How do I iterate over the rows of this dataframe? For every row, I want to access its elements (values in cells) by the name of the columns. For example:
for row in…
Roman
- 124,451
- 167
- 349
- 456