Question

this is more like a puzzle. I wanted to know if there is a way to choose k random items from a list of n items, given that n is unknown, and I only want to read the list of items once.

Thank you

Answer 1

I guess the answer to my question is this:

pick first k elements and store them into an array of length k
for each element x > k
   insert x with probability k/x
   choose position at random between 1 and k