Recursion Help

Question

Ok, Our Assignment is, find the kth smallest item in an array using recursion. I have been reading the text, and it says that I need to have a "pivot point" somewhere in the array and then sort each array on either side of the pivot. Right now, I have picked out a pivot which is pretty much in the middle of the array not matter how big it is. Now I am trying to make two separate arrays, one array that is from index 0 of the array to the pivot -1 and another array that is from pivot + 1 to the last index of the array. After that I think I will try to use some kind of sort method to sort each of the smaller arrays. Anyhow, right now I am stuck on making the new array, from 0 to pivot - 1. If you need more explanation of what I am trying to do, please ask. An example would be: if I make my array from 0 - 999, my pivot would be 499 and I am trying to make a new array from 0 - 498 (this excludes the pivot). When I test my program, it gives me an error saying the array is out of bounds, I have kinda a clue what the means but I just cant figure out why it is happening, and I strongly feel it has something to do with this code I am showing you. I am wondering about my base case as well, could there be something wrong with the base case? If this makes no sense, I will try to answer your questions, or if that does not work I will post the whole code, but I am trying to refrain from posting the whole code due to other classmates might be on here stealing my code! Thanks in advance
public static int[] arrPartition1(int[] fillerArr, int first, int pivotInd){
         int[] firstHalfArray;
         firstHalfArray = new int[pivotInd - 1];
         if(first < pivotInd - 1)
              return firstHalfArray;
         if(first < pivotInd)
              firstHalfArray[first] = fillerArr[first];
              first++;
              return arrPartition1(fillerArr, first, pivotInd);
    }

Answer 1

and here is my whole program. it compiles, but there is the runtime error. and i am kind of clueless on what i am doing wrong here -
import java.util.*;
public class TEST
   public static void main(String[] args)
      Scanner scan = new Scanner(System.in);
      int n = 10;
      int k = 2;
      int first = 0;
      int last = 0;
      int kth = 0;
//      n = scan.nextInt();
//      k = scan.nextInt();
      int[] dA = new int[n];
      for(int i=0; i<n ; i++)
      dA[i] = (int) Math.round(1000*Math.random());
      System.out.println("array elements:" + dA);
first = 0;
last = n-1;
quickSort(dA, first, last);
for(int i=0; i<n; i++)
System.out.println("sorted array: entry at "+i+" :" +dA[i]);
// kth = kSmall(k, dA, first, last);
// System.out.println(kth);
public static void quickSort(int[] dA, int first, int last)
int pivotIndex =1 ;
// if(last<= first)
// return;
if(first<last)
quickSort(dA, first, pivotIndex-1);
quickSort(dA, pivotIndex+1, last);
public static int kSmall(int k, int[] dA, int first, int last)
int pivotIndex = 5;
if(k < (pivotIndex - first + 1))
return kSmall(k, dA, first, pivotIndex-1);
else if(k==(pivotIndex-first+1))
return dA[pivotIndex];
else
return kSmall(k-(pivotIndex-first+1), dA, pivotIndex+1, last);
Edited by: aberrated on Feb 9, 2008 9:47 PM