static void shellsort(int[] A) {
  for (int i=A.length/2; i>2; i/=2) { // For each increment
    for (int j=0; j<i; j++) {         // Sort each sublist
      inssort2(A, j, i);
    }
  }
  inssort2(A, 0, 1);     // Could call regular inssort here
}

/** Modified Insertion Sort for varying increments */
static void inssort2(int[] A, int start, int incr) {
  for (int i=start+incr; i<A.length; i+=incr)
    for (int j=i; (j>=incr) && (A[j] < A[j-incr]); j-=incr)
      Swap.swap(A, j, j-incr);
}

static void quicksort(Comparable[] A, int i, int j) { // Quicksort
  int pivotindex = findpivot(A, i, j);  // Pick a pivot
  Swap.swap(A, pivotindex, j);               // Stick pivot at end
  // k will be the first position in the right subarray
  int k = partition(A, i, j-1, A[j]);
  Swap.swap(A, k, j);                        // Put pivot in place
  if ((k-i) > 1) { quicksort(A, i, k-1); }  // Sort left partition
  if ((j-k) > 1) { quicksort(A, k+1, j); }  // Sort right partition
}

static int findpivot(Comparable[] A, int i, int j)
  { return (i+j)/2; }