boolean delete(Object x, int parentIndex) {
int i = childToInsertAt(x, true);
int priorParentIndex = parentIndex;
BTreeNode temp = this;
if (i != -1) {
do {
if (temp.entries[i] == null || temp.entries[i].child == null) return false;
temp = temp.entries[i].child;
priorParentIndex = parentIndex;
parentIndex = i;
i = temp.childToInsertAt(x, true);
} while (i != -1);
} // Now temp contains element to delete and temp's parentIndex is parentIndex
if (temp.isLeaf()) { // If leaf and have more than MIN elements, simply delete
if (temp.nrElements > MIN) {
temp.deleteElement(x);
BTreeSet.this.size--;
return true;
}
// else - If leaf and have less than MIN elements, than prepare the BTreeSet for deletion
temp.prepareForDeletion(parentIndex);
temp.deleteElement(x);
BTreeSet.this.size--;
temp.fixAfterDeletion(priorParentIndex);
return true;
}
// else - Only delete at leaf so first switch with successor than delete
temp.switchWithSuccessor(x);
parentIndex = temp.childToInsertAt(x, false) + 1;
return temp.entries[parentIndex].child.delete(x, parentIndex);
}
private Object nextElement() {
if (currentNode.isLeaf()) {
if (index < currentNode.nrElements) return currentNode.entries[index++].element;
else if (!parentIndex
.empty()) { // All elements have been returned, return successor of lastReturned if it
// exists
currentNode = currentNode.parent;
index = ((Integer) parentIndex.pop()).intValue();
while (index == currentNode.nrElements) {
if (parentIndex.empty()) break;
currentNode = currentNode.parent;
index = ((Integer) parentIndex.pop()).intValue();
}
if (index == currentNode.nrElements)
return null; // Reached root and he has no more children
return currentNode.entries[index++].element;
} else { // Your a leaf and the root
if (index == currentNode.nrElements) return null;
return currentNode.entries[index++].element;
}
}
// else - You're not a leaf so simply find and return the successor of lastReturned
currentNode = currentNode.entries[index].child;
parentIndex.push(Integer.valueOf(index));
while (currentNode.entries[0].child != null) {
currentNode = currentNode.entries[0].child;
parentIndex.push(Integer.valueOf(0));
}
index = 1;
return currentNode.entries[0].element;
}
