Quick sort with median-of-three partitioning : Sort Search « Collections Data Structure « Java

Quick sort with median-of-three partitioning

Quick sort with median-of-three partitioning
public class AnotherQuickSort {
  private long[] data;

  private int len;

  public AnotherQuickSort(int max) {
    data = new long[max];
    len = 0;

  public void insert(long value) {
    data[len] = value; // insert and increment size

  public void display() {
    for (int j = 0; j < len; j++)
      System.out.print(data[j] + " ");

  public void quickSort() {
    recQuickSort(0, len - 1);

  public void recQuickSort(int left, int right) {
    int size = right - left + 1;
    if (size <= 3) // manual sort if small
      manualSort(left, right);
    else // quicksort if large
      long median = medianOf3(left, right);
      int partition = partitionIt(left, right, median);
      recQuickSort(left, partition - 1);
      recQuickSort(partition + 1, right);

  public long medianOf3(int left, int right) {
    int center = (left + right) / 2;
    // order left & center
    if (data[left] > data[center])
      swap(left, center);
    // order left & right
    if (data[left] > data[right])
      swap(left, right);
    // order center & right
    if (data[center] > data[right])
      swap(center, right);

    swap(center, right - 1); // put pivot on right
    return data[right - 1]; // return median value

  public void swap(int dex1, int dex2) {
    long temp = data[dex1];
    data[dex1] = data[dex2];
    data[dex2] = temp;

  public int partitionIt(int left, int right, long pivot) {
    int leftPtr = left; // right of first elem
    int rightPtr = right - 1; // left of pivot

    while (true) {
      //       find bigger
      while (data[++leftPtr] < pivot)
      //       find smaller
      while (data[--rightPtr] > pivot)

      if (leftPtr >= rightPtr) // if pointers cross, partition done
        // not crossed, so
        swap(leftPtr, rightPtr); // swap elements
    swap(leftPtr, right - 1); // restore pivot
    return leftPtr; // return pivot location

  public void manualSort(int left, int right) {
    int size = right - left + 1;
    if (size <= 1)
      return; // no sort necessary
    if (size == 2) { // 2-sort left and right
      if (data[left] > data[right])
        swap(left, right);
    } else // size is 3
    { // 3-sort left, center, & right
      if (data[left] > data[right - 1])
        swap(left, right - 1); // left, center
      if (data[left] > data[right])
        swap(left, right); // left, right
      if (data[right - 1] > data[right])
        swap(right - 1, right); // center, right

  public static void main(String[] args) {
    int maxSize = 16; 
    AnotherQuickSort arr = new AnotherQuickSort(maxSize); 

    for (int j = 0; j < maxSize; j++) { // random numbers
      long n = (int) (java.lang.Math.random() * 99);


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