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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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How do I check to see if a value is an integer in MySQL?
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Get statistics for each group (such as count, mean, etc) using pandas GroupBy?
...gation methods at once. This should give you the result you need:
df[['col1', 'col2', 'col3', 'col4']].groupby(['col1', 'col2']).agg(['mean', 'count'])
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How to count the frequency of the elements in an unordered list?
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numpy: most efficient frequency counts for unique values in an array
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Fastest way to iterate over all the chars in a String
...e now Java will store strings as byte[] by default.
SECOND UPDATE: As of 2016-10-25, on my AMDx64 8core and source 1.8, there is no difference between using 'charAt' and field access. It appears that the jvm is sufficiently optimized to inline and streamline any 'string.charAt(n)' calls.
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Index all *except* one item in python
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For a list, you could use a list comp. For example, to make b a copy of a without the 3rd ele...
How to initialize an array in one step using Ruby?
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You can use an array literal:
array = [ '1', '2', '3' ]
You can also use a range:
array = ...
Drop rows with all zeros in pandas data frame
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Convert Elixir string to integer or float
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Check Integer.parse/1 and Float.parse/1.
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