/**
* @brief AVL tree delete one node. This method is to find its front data child,
* means its first left-right child to cover its data value, and replace to
* remove the child node. The verbose analysis is the following.
* if pT has single child or no, then remove pT and attach its child to its
* parent, now his parent bf --, and require rebalance it.
* elseif pT has two child, find the front data child, means its first left-right
* child, and copy the data in pT, and begin to remove this node named Y. As we
* know Y has no child or single left child, so we can attach the child to Y's
* parent. And then require rebalance from Y's parent to pT.
* May be the Y should split 2 situation:
* 1. the Y is the pT's lchild.
* 2. the Y is the pT's lchild's grand right son.
*
* @param pT tree quote point.
* @param plower output tree becomes lower or not.
*/
PRIVATE void _avl_deletenode(TREE* pT, int* plower) {
if (NULL == (*pT)->lchild) {
NODE* Y = (*pT); (*pT) = (*pT)->rchild; (*plower) = 1; free(Y);
} else if (NULL == (*pT)->rchild) {
NODE* Y = (*pT); (*pT) = (*pT)->lchild; (*plower) = 1; free(Y);
} else { // (*pT)->lchild and (*pT)->rchild are all not null.
NODE* Y = (*pT)->lchild;
if (NULL == Y->rchild) {
ELEMENT_COPY((*pT)->data, Y->data);
(*pT)->lchild = Y->lchild; (*plower) = 1; free(Y);
_avl_left_lower_rebalance(pT, plower);
} else { // NULL != Y->rchild
AVLTREE_STACK* TS = NULL;
tree_stack_push(&TS, &((*pT)->lchild));
while (Y->rchild) {
if (Y->rchild->rchild) { tree_stack_push(&TS, &(Y->rchild)); }
Y = Y->rchild;
}
/// copy data to pT node and delete Y node
ELEMENT_COPY((*pT)->data, Y->data);
TREE* YF = tree_stack_front(&TS);
(*YF)->rchild = Y->lchild;
(*plower) = 1; free(Y);
// pop all parent line and right lower rabalance
while (NULL != (YF = tree_stack_pop(&TS))) {
if (0 == (*plower)) { continue; }
_avl_right_lower_rebalance(YF, plower);
}
// finally do left lower rebalance if lower from left subtree
if (1 == (*plower)) { _avl_left_lower_rebalance(pT, plower); }
}
}
}
static int tree_item_circular(tree_item_t *item)
{
if ( item == NULL )
return 0;
if ( tree_object_circular(item->object) ) {
tree_stack_push(item->parent_tree, item->object);
return 1;
}
return 0;
}
