Finding Kth smallest element in an unsorted Array?

Question

Given an unsorted array of elements I want to findout the Kth smallest element in the array. Can someone help me with the approach and code.

Answer 1

1. Divide the array in to n/5 lists of 5 elements each.
2. Find the median in each sub array of 5 elements.
3. Recursively find the median of all the medians, lets call it M
4. Partition the array in to two sub array 1st sub-array contains the elements larger than M , lets say this sub-array is a1 , while other sub-array contains the elements smaller then M., lets call this sub-array a2.
5. If k <= |a1|, return selection (a1,k).
6. If k− 1 = |a1|, return M.
7. If k> |a1| + 1, return selection(a2,k −a1 − 1).

Complexity: o(n)

Source: http://cs.indstate.edu/~spitla/abstract2.pdf