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Fast permutation -> number -> permutation mapping algorithms
I have n elements. For the sake of an example, let's say, 7 elements, 1234567. I know there are 7! = 5040 permutations possible of these 7 elements.
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Transpose list of lists
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How about
map(list, zip(*l))
--> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
For python 3.x users can use
list(map(list, zip(*l)))
Explanation:
There are two things we need to know to understand what's going on:
The signature of zip: zip(*iterables) This means zip expects ...
JavaScript math, round to two decimal places [duplicate]
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824
NOTE - See Edit 4 if 3 digit precision is important
var discount = (price / listprice).toFixed(...
Installing Numpy on 64bit Windows 7 with Python 2.7.3 [closed]
...nstaller for Numpy is for Numpy version 1.3.0 which only works with Python 2.6
6 Answers
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What does the tilde (~) mean in my composer.json file?
...de means next significant release. In your case, it is equivalent to >= 2.0, < 3.0.
The full explanation is at Tilde Version Range docs page:
The ~ operator is best explained by example: ~1.2 is equivalent to >=1.2 <2.0.0, while ~1.2.3 is equivalent to >=1.2.3 <1.3.0.
Ano...
Rotating a two-dimensional array in Python
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Consider the following two-dimensional list:
original = [[1, 2],
[3, 4]]
Lets break it down step by step:
>>> original[::-1] # elements of original are reversed
[[3, 4], [1, 2]]
This list is passed into zip() using argument unpacking, so the zip call ends up...
Scratch还是App Inventor？低代码编程工具2026终极横评：谁才是真正的入门...
Scratch还是App Inventor？低代码编程工具2026终极横评：谁才是真正的入门之王
十年前，"学编程"意味着啃厚厚的C语言教材；到了2026年，低代码和可视化编程工具已经彻底重塑了编程教育的格局。无论你是想给孩子找一门...
How many double numbers are there between 0.0 and 1.0?
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Java doubles are in IEEE-754 format, therefore they have a 52-bit fraction; between any two adjacent powers of two (inclusive of one and exclusive of the next one), there will therefore be 2 to the 52th power different doubles (i.e., 4503599627370496 of them). For example, that's the...
counting number of directories in a specific directory
...* -maxdepth 0 -type d | wc -l
11
$ find .vim/ -maxdepth 1 -type d | wc -l
12
You can also use ls:
$ ls -l .vim | grep -c ^d
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$ ls -l .vim
total 52
drwxrwxr-x 3 anossovp anossovp 4096 Aug 29 2012 after
drwxrwxr-x 2 anossovp anossovp 4096 Aug 29 2012 autoload
drwxrwxr-x 13 anossovp anossovp...
Rspec: “array.should == another_array” but without concern for order
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265
Try array.should =~ another_array
The best documentation on this I can find is the code itsel...