How to generate subsets of an array - Inside code

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This will definitely be useful some day after university. Thanks!
Tried all of these in Ruby. You could replace the string-conversion in the second approach with a few shifts and bit-ands.
Here is my list, sorted by speed (List was 20 elements long, ran each 25 times in jruby):
1. Your 3rd approach (300ms)
2. My version of the 3rd approach (Similar but with more explicit copying) (530ms)
3. 1st approach (recursive) (780ms)
4. 2nd approach without strings but shifts and & instead. (3100ms)
5. 2nd approach with strings. (6500ms)
Let this be a warning to all: Even if a solution looks smart, it might not be the best and if it looks horrible, it might not be too bad.

TheDarkOne

deserves 1million views. Thanks a lot. Great animation

mohammedhajomar

Second solution is Classic. Thank you, Bro. Request to make algorithmic problems like this.

satyajitdas

My solution in Haskell is just 4 lines:

subsets :: [a] -> [[a]]
subsets [] = [[]]
subsets (x:xs) =
subsets xs ++ map (x:) (subsets xs)

xRyann_

I wasted a lot of time understanding it, thanks to this amazing video I finally understood :).

DheerajKumar-fnzq

You finally explained it the correct way. Take for example the classic CCI, where they say that subset can be generated with your method (3) and then they code up the method (1). Like, wth why? You are the only one (aside from neet code) that has the code matching up to the explanation. Many build a tree and then use code that clearly doesnt generate that tree.

luigicennini