@Test
public void testSort() {
String[] sortable = {"S", "O", "R", "T", "E", "X", "A", "M", "P", "L", "E"};
String[] sorted = {"A", "E", "E", "L", "M", "O", "P", "R", "S", "T", "X"};
Insertion.sort(sortable);
assertEquals(sorted, sortable);
}
private static void sort(Comparable[] a, int lo, int hi) {
int N = hi - lo + 1;
if (N <= CUT_OFF) {
Insertion.sort(a, lo, hi);
return;
} else if (N <= 40) {
int m = median3(a, lo, lo + N / 2, hi);
exch(a, m, lo);
}
// use Tukey ninther as partitioning element
else {
int eps = N / 8;
int mid = lo + N / 2;
int m1 = median3(a, lo, lo + eps, lo + eps + eps);
int m2 = median3(a, mid - eps, mid, mid + eps);
int m3 = median3(a, hi - eps - eps, hi - eps, hi);
int ninther = median3(a, m1, m2, m3);
exch(a, ninther, lo);
}
// Bentley-McIlroy 3-way partitioning
int i = lo, j = hi + 1;
int p = lo, q = hi + 1;
Comparable v = a[lo];
while (true) {
while (less(a[++i], v)) if (i == hi) break;
while (less(v, a[--j])) if (j == lo) break;
if (i >= j) break;
exch(a, i, j);
if (eq(a[i], v)) exch(a, ++p, i);
if (eq(a[j], v)) exch(a, --q, j);
}
exch(a, lo, j);
i = j + 1;
j = j - 1;
for (int k = lo + 1; k <= p; k++) exch(a, k, j--);
for (int k = hi; k >= q; k--) exch(a, k, i++);
sort(a, lo, j);
sort(a, i, hi);
}