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Why is XOR the default way to combine hashes?
Say you have two hashes H(A) and H(B) and you want to combine them. I've read that a good way to combine two hashes is to XOR them, e.g. XOR( H(A), H(B) ) .
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How to get line count of a large file cheaply in Python?
I need to get a line count of a large file (hundreds of thousands of lines) in python. What is the most efficient way both memory- and time-wise?
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Is it possible to change only the alpha of a rgba background colour on hover?
I have a set of <a> tags with differing rgba background colours but the same alpha. Is it possible to write a single css style that will change only the opacity of the rgba attribute?
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How to extract the decision rules from scikit-learn decision-tree?
Can I extract the underlying decision-rules (or 'decision paths') from a trained tree in a decision tree as a textual list?
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How to initialize a two-dimensional array in Python?
I'm beginning python and I'm trying to use a two-dimensional list, that I initially fill up with the same variable in every place. I came up with this:
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JS Client-Side Exif Orientation: Rotate and Mirror JPEG Images
Digital camera photos are often saved as JPEG with an EXIF "orientation" tag. To display correctly, images need to be rotated/mirrored depending on which orientation is set, but browsers ignore this information rendering the image. Even in large commercial web apps, support for EXIF orientation can ...
How do I replace NA values with zeros in an R dataframe?
I have a data frame and some columns have NA values.
21 Answers
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What are the mathematical/computational principles behind this game?
My kids have this fun game called Spot It! The game constraints (as best I can describe) are:
9 Answers
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How do you rotate a two dimensional array?
Inspired by Raymond Chen's post , say you have a 4x4 two dimensional array, write a function that rotates it 90 degrees. Raymond links to a solution in pseudo code, but I'd like to see some real world stuff.
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How do I get indices of N maximum values in a NumPy array?
NumPy proposes a way to get the index of the maximum value of an array via np.argmax .
16 Answers
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