快速排序

package sort;

public class Quicksort { 
public static void main(String[] args) {

  int[] s = { 13, 15, 7, 10, 20, 4, 8, 19 };
  // s = quicksort(s, 0, s.length - 1);
  s = quicks(s, 0, s.length - 1);
  for (int i : s) {

   System.out.print(i + " ");
  }

}

public static int[] quickd(int[] num, int left, int right) {
  if (left < right) {
   int k = doublequick(num, left, right);
   System.out.println("k=" + k);
   quickd(num, left, k - 1);
   quickd(num, k + 1, right);
  }
  return num;
}

public static int[] quicks(int[] num, int left, int right) {
  if (left < right) {
   int k = singlequick(num, left, right);
   System.out.println("k=" + k);
   quicks(num, left, k - 1);
   quicks(num, k + 1, right);
  }
  return num;
}


public static int doublequick(int[] s, int left, int right) {
  int i = left;
  int j = right;
  int temp;
  int x = s[i];
  while (i < j) {
   while (i < j && s[j] >= x)
    j--;
   temp = s[j];
   s[j] = s[i];
   s[i] = temp;
   while (i < j && s[i] <= x)
    i++;
   temp = s[j];
   s[j] = s[i];
   s[i] = temp;
  }

  return i;

}
 
public static int singlequick(int[] s, int left, int right) {
  int i = left;
  int j = right;
  int x = s[left];
  while (i < j) {
   while (i < j && s[j] >= x)
    j--;
   s[i] = s[j];
   while (i < j && s[i] <= x)
    i++;
   s[j] = s[i];
  }
  s[i] = x;
  System.out.println("i=" + i);
  return i;
}
  
public static int[] quicksort(int[] s, int left, int right) {

  int i = left;
  int j = right;
  int middle = s[(i + j) / 2];
  System.out.println(middle);
  do {
   while (i <= right && middle > s[i])
    i++;
   while (j >= left && middle < s[j])
    j--;

   if (i <= j) {
  
    int temp = s[j];
    s[j] = s[i];
    s[i] = temp;
    i++;
    j--;

   }

  } while (i <= j);

  for (int k : s) {

   System.out.print(k + " ");
  }

  if (left < j) {


   System.out.println("j=" + j);
   quicksort(s, left, j);

  }
  if (right > i) {
 
   System.out.println("i=" + i);
   quicksort(s, i, right);

  }

  return s;

}
}