public static Node delete(
Object token, NodeStack stack, Node root, Object key, Comparator comparator) {
if (Debug) {
token = new Object();
validate(null, root);
}
if (root == Null) {
return root;
} else if (root.left == Null && root.right == Null) {
if (Compare.equal(key, root.key, comparator)) {
return Null;
} else {
return root;
}
}
stack = new NodeStack(stack);
Node newRoot = getNode(token, root);
Node old = root;
Node new_ = newRoot;
while (old != Null) {
if (key == null) throw new NullPointerException();
if (old.key == null) {
throw new NullPointerException();
}
int difference = Compare.compare(key, old.key, comparator);
if (difference < 0) {
stack.push(new_);
old = old.left;
new_ = new_.left = getNode(token, old);
} else if (difference > 0) {
stack.push(new_);
old = old.right;
new_ = new_.right = getNode(token, old);
} else {
break;
}
}
if (old == Null) {
if (stack.top.left == new_) {
stack.top.left = Null;
} else {
stack.top.right = Null;
}
stack.popStack();
return root;
}
Node dead;
if (new_.left == Null || new_.right == Null) {
dead = new_;
} else {
successor(token, new_, stack);
dead = stack.top;
stack.pop();
}
Node child;
if (dead.left != Null) {
child = getNode(token, dead.left);
} else if (dead.right != Null) {
child = getNode(token, dead.right);
} else {
child = Null;
}
if (stack.top == null) {
child.red = false;
stack.popStack();
if (Debug) {
validate(root, child);
}
return child;
} else if (dead == stack.top.left) {
stack.top.left = child;
} else {
stack.top.right = child;
}
if (dead != new_) {
new_.key = dead.key;
new_.value = dead.value;
}
if (!dead.red) {
// rebalance
while (stack.top != null && !child.red) {
if (Debug) checkArgument(stack.top.token == token);
if (child == stack.top.left) {
Node sibling = stack.top.right = getNode(token, stack.top.right);
if (sibling.red) {
if (Debug) checkArgument(sibling.token == token);
sibling.red = false;
stack.top.red = true;
Node n = leftRotate(token, stack.top);
if (stack.index == stack.base) {
newRoot = n;
} else if (stack.peek().right == stack.top) {
if (Debug) checkArgument(stack.peek().token == token);
stack.peek().right = n;
} else {
if (Debug) checkArgument(stack.peek().token == token);
stack.peek().left = n;
}
Node parent = stack.top;
stack.top = n;
stack.push(parent);
sibling = stack.top.right = getNode(token, stack.top.right);
}
if (!(sibling.left.red || sibling.right.red)) {
if (Debug) checkArgument(sibling.token == token);
sibling.red = true;
child = stack.top;
stack.pop();
} else {
if (!sibling.right.red) {
sibling.left = getNode(token, sibling.left);
sibling.left.red = false;
if (Debug) checkArgument(sibling.token == token);
sibling.red = true;
sibling = stack.top.right = rightRotate(token, sibling);
}
if (Debug) checkArgument(sibling.token == token);
sibling.red = stack.top.red;
stack.top.red = false;
sibling.right = getNode(token, sibling.right);
sibling.right.red = false;
Node n = leftRotate(token, stack.top);
if (stack.index == stack.base) {
newRoot = n;
} else if (stack.peek().right == stack.top) {
if (Debug) checkArgument(stack.peek().token == token);
stack.peek().right = n;
} else {
if (Debug) checkArgument(stack.peek().token == token);
stack.peek().left = n;
}
child = newRoot;
stack.clear();
}
} else {
// this is just the above code with left and right swapped:
Node sibling = stack.top.left = getNode(token, stack.top.left);
if (sibling.red) {
if (Debug) checkArgument(sibling.token == token);
sibling.red = false;
stack.top.red = true;
Node n = rightRotate(token, stack.top);
if (stack.index == stack.base) {
newRoot = n;
} else if (stack.peek().left == stack.top) {
if (Debug) checkArgument(stack.peek().token == token);
stack.peek().left = n;
} else {
if (Debug) checkArgument(stack.peek().token == token);
stack.peek().right = n;
}
Node parent = stack.top;
stack.top = n;
stack.push(parent);
sibling = stack.top.left = getNode(token, stack.top.left);
}
if (!(sibling.right.red || sibling.left.red)) {
if (Debug) checkArgument(sibling.token == token);
sibling.red = true;
child = stack.top;
stack.pop();
} else {
if (!sibling.left.red) {
sibling.right = getNode(token, sibling.right);
sibling.right.red = false;
if (Debug) checkArgument(sibling.token == token);
sibling.red = true;
sibling = stack.top.left = leftRotate(token, sibling);
}
if (Debug) checkArgument(sibling.token == token);
sibling.red = stack.top.red;
stack.top.red = false;
sibling.left = getNode(token, sibling.left);
sibling.left.red = false;
Node n = rightRotate(token, stack.top);
if (stack.index == stack.base) {
newRoot = n;
} else if (stack.peek().left == stack.top) {
if (Debug) checkArgument(stack.peek().token == token);
stack.peek().left = n;
} else {
if (Debug) checkArgument(stack.peek().token == token);
stack.peek().right = n;
}
child = newRoot;
stack.clear();
}
}
}
if (Debug) checkArgument(child.token == token);
child.red = false;
}
stack.popStack();
if (Debug) {
validate(root, newRoot);
}
return newRoot;
}
static {
Null.left = Null;
Null.right = Null;
Null.value = Null;
}