@Override
TrieNode delete(final int h, final Item k, final int l, final InputInfo ii)
throws QueryException {
final int key = key(h, l);
final TrieNode sub = kids[key];
if (sub == null) return this;
final TrieNode nsub = sub.delete(h, k, l + 1, ii);
if (nsub == sub) return this;
final int nu;
if (nsub == null) {
nu = used ^ 1 << key;
if (Integer.bitCount(nu) == 1) {
final TrieNode single = kids[Integer.numberOfTrailingZeros(nu)];
// check whether the child depends on the right offset
if (!(single instanceof TrieBranch)) return single;
}
} else nu = used;
final TrieNode[] ks = copyKids();
ks[key] = nsub;
return new TrieBranch(ks, nu, size - 1);
}
