Thread: QuickSelect Help

I'm work on the quickSelect algorithm to find the kth smallest integer however I keep getting the java.lang.ArrayIndexOutOfBoundsException error.

import java.io.*;
import java.lang.ArrayIndexOutOfBoundsException;
import java.util.Random;
 
public class QSelect {
 
    public static void main(String[] args){
        int n = 16;
        int[] array = new int[n];
        Random random = new Random();
 
        for(int i = 0; i < n; i++){
            array[i] = random.nextInt(33);
        }
 
        int k = array.length/2;
 
        System.out.println(java.util.Arrays.toString(array));
        System.out.println("K = " + k + "\n");
 
        int count = quickSelect(array, 0, array.length-1, k);
    }
 
    static int quickSelect(int[] array, int low, int high, int k){
        int i = low, j = high;
        int count = 0;
 
        int p = array[low + (high-low)/2];
        int pivotIndex = low + (high-low)/2;
 
        System.out.println("Pivot: " + p);
        // Divide into two lists
        while (i <= j) {
 
          //i increments until it is greater than the pivor
 
          while (array[i] < p) {
            i++;
            count++;
          }
 
          //j decrements untili it is smaller than
 
          while (array[j] > p) {
            j--;
            count++;
          }
 
          /*
           * When the elements in i are greater or equal to j
           * they swap values
           */
          count++;
          if (i <= j) {
            System.out.println("Swapping " + i + " and " + j);
 
            //keeps track of pivot position
            if(i == pivotIndex){
            pivotIndex = j;
        }
            else if(j == pivotIndex){
            pivotIndex = i;
        }
 
            swap(array, i, j, pivotIndex);
            System.out.println("Pivot Index: " + pivotIndex);
            i++;
            j--;
          }
          System.out.println(java.util.Arrays.toString(array));
        }
        System.out.println("Pivot Index: " + pivotIndex);
 
        if(pivotIndex == k-1)
            System.out.println(p + " is the kth Smallest.");
        else if(pivotIndex > (low + (k-1))){
            int[] a2 = new int[pivotIndex-1];     //create a subarray for smaller comparables
            for(int x = 0; x <=pivotIndex; x++){
                a2[x] = array[x];
            }
            count += quickSelect(a2, 0, a2.length-1, k);
        }
        else{
            int[] a3 = new int[array.length - (pivotIndex+1)];      //create a subarray for larger comparables
            for(int y = 0; y < a3.length; y++){
                a3[y] = array[y];
            }
            count += quickSelect(a3, 0, a3.length, k);
        }
        //j++;
        //System.out.println(j);
 
        return count;
    }
 
    static int swap(int[] array, int i, int j, int pivotIndex) {
        int temp = array[i];
 
        array[i] = array[j];
        array[j] = temp;
 
        return pivotIndex;
  }
}

The code works fine up until the if statements which compare the pivot position (pivotIndex) to k. It's here where I'm getting the error. I'm not exactly sure how I'm going outside of the array or if I completely botched this part of the code. Any hints?

Yeah the error message is:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 13
at qselect.QSelect.quickSelect(QSelect.java:91)
at qselect.QSelect.main(QSelect.java:33)

Ok thanks! I think I got it.