import java.util.Collections;
import java.util.ArrayList;
import java.util.Random;

/** Array.java - do all the heavy lifting for the Randomized Quick Select
 *  algorithm.  Store the numbers from 1 to n.  I think the implementation
 *  is easier if we use ArrayList as the underlying representation of data.
 *  The numbers will be shuffled using Java's built-in shuffler.
 *  Then, to do the select algorithm, we assume we want the k-th SMALLEST
 *  number, which should wind up being k.  
 *  For a given "Array" instance, you could use different values of k,
 *  so I have decided not to declare k as an attribute of the class.
 *  However, note that when we count operations, we need to start the count
 *  over every time we begin a new select.
 *  Since the RQS algorithm needs a random number generator, we'll just
 *  make it an attribute of our "Array" as well.
 */
public class Array
{
  private ArrayList<Integer> S;
  private int ops;
  private Random gen;

  public Array(int size)
  {
    gen = new Random();
    S = new ArrayList<Integer>();
    for (int i = 1; i <= size; ++i)
      S.add(new Integer(i));

    Collections.shuffle(S);
  }

  /** A wrapper function to begin the Randomized Quick Select Algorithm.
   *  Every time we begin a brand new select problem, we need to set the
   *  number of counted operations to 0.
   */
  public int rqs(int k)
  {
    ops = 2;

    // Call the recursive function.
    int result = quickSelect(S, k);
    return result;
  }

  /** This is the recursive function that performs the quickSelect()
   *  function suggested by the class notes.  Here's the pseudocode:
   *  quickSelect(S, k):
   *    if n = 1
   *      return S[1]
   *    x = random element from S
   *    L = [ all elements < x ]
   *    E = [ all elements == x ]
   *    G = [ all elements > x ]
   *    if k <= |L|
   *      return quickSelect(L,k)
   *    else if k <= |L| + |E|
   *      return x
   *    else
   *      return quickSelect(G, k - |L| - |E|)
   *      // e.g. 12th out of 20 = 2nd out of 10
   */
  private int quickSelect(ArrayList<Integer> listS, int k)
  {
    //////////////////////////////////////////////////////////
    // Take out the return 0, and insert your implementation.
    //////////////////////////////////////////////////////////

    return 0;
  }

  public int getOps()
  {
    return ops;
  }
}