private E findStartingNodeForDeletion(E element) {
if (root == null) return null;
TreeNode<E> parent = null;
TreeNode<E> current = root;
while (current != null) {
if (element.compareTo(current.element) < 0) {
parent = current;
current = current.left;
} else if (element.compareTo(current.element) > 0) {
parent = current;
current = current.right;
} else break;
}
if (current == null) return null;
if (current.left == null) {
if (parent == null) {
return null;
} else {
return parent.element;
}
} else {
TreeNode<E> parentOfRightMost = current;
TreeNode<E> rightMost = current.left;
while (rightMost.right != null) {
parentOfRightMost = rightMost;
rightMost = rightMost.right;
}
return parentOfRightMost.element;
}
}
public boolean delete(E element) {
if (root == null) return false;
TreeNode<E> parent = null;
TreeNode<E> current = root;
while (current != null) {
if (element.compareTo(current.element) < 0) {
parent = current;
current = current.left;
} else if (element.compareTo(current.element) > 0) {
parent = current;
current = current.right;
} else break;
}
if (current == null) return false;
if (current.left == null) {
if (parent == null) {
root = current.right;
} else {
if (element.compareTo(parent.element) < 0) parent.left = current.right;
else parent.right = current.right;
balancePath(parent.element);
}
} else {
TreeNode<E> parentOfRightMost = current;
TreeNode<E> rightMost = current.left;
while (rightMost.right != null) {
parentOfRightMost = rightMost;
rightMost = rightMost.right;
}
current.element = rightMost.element;
if (parentOfRightMost.right == rightMost) parentOfRightMost.right = rightMost.left;
else parentOfRightMost.left = rightMost.left;
balancePath(parentOfRightMost.element);
}
size--;
return true;
}