Find the x smallest integers in a list of length n

Question

You have a list of n integers and you want the x smallest. For example,

x_smallest([1, 2, 5, 4, 3], 3) should return [1, 2, 3].

I\'ll v

Answer 1

Maintain the list of the x highest so far in sorted order in a skip-list. Iterate through the array. For each element, find where it would be inserted in the skip list (log x time). If in the interior of the list, it is one of the smallest x so far, so insert it and remove the element at the end of the list. Otherwise do nothing.

Time O(n*log(x))

Alternative implementation: maintain the collection of x highest so far in a max-heap, compare each new element with top element of the heap, and pop + insert new element only if the new element is less than the top element. Since comparison to top element is O(1) and pop/insert O(log x), this is also O(nlog(x))