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 void fixAfterDeletion(int parentIndex) {
if (isRoot() || parent.isRoot()) return; // No fixing needed
if (parent.nrElements < MIN) { // If parent lost it's n/2 element repair it
BTreeNode temp = parent;
temp.prepareForDeletion(parentIndex);
if (temp.parent == null) return; // Root changed
if (!temp.parent.isRoot() && temp.parent.nrElements < MIN) { // If need be recurse
BTreeNode x = temp.parent.parent;
int i = 0;
// Find parent's parentIndex
for (; i < entries.length; i++) if (x.entries[i].child == temp.parent) break;
temp.parent.fixAfterDeletion(i);
}
}
}