// partitions the array using the first element as pivot
public static int partition(final int a[], final int lo, final int hi) {
int i = lo;
int j = hi + 1;
while (true) {
while (a[++i] < a[lo]) {
if (i == hi) {
break;
}
}
while (a[--j] > a[lo]) {
if (j == lo) {
break;
}
}
if (i >= j) {
break;
}
IntUtils.swap(a, i, j);
}
IntUtils.swap(a, lo, j);
// System.out.println("j="+j);
return j;
}
public static void threeWayQuickSort(final int a[], final int lo, final int hi) {
if (lo > hi) {
return;
}
final int pivot = a[lo];
int lt = lo;
int gt = hi;
int i = lo;
while (i <= gt) {
if (pivot > a[i]) {
IntUtils.swap(a, i++, lt++);
} else if (pivot < a[i]) {
IntUtils.swap(a, i, gt--);
} else {
i++;
}
}
threeWayQuickSort(a, lo, lt - 1);
threeWayQuickSort(a, gt + 1, hi);
}
