static AVLNode* rebalanceNode(AVLNode *node){
assert(node != nullptr); // should not be called otherwise
if(isBalanced(node)) return node;
if(leftHeight(node) < rightHeight(node)) return rightRebalanceNode(node);
if(rightHeight(node) < leftHeight(node)) return leftRebalanceNode(node);
// should not reach this point
assert(false);
}
static void updateHeight(AVLNode *node){
assert(node != nullptr); // should not be called otherwise
int lh = leftHeight(node);
int rh = rightHeight(node);
int max = (lh > rh) ? lh : rh;
node->setHeight(1 + max);
}
static bool isBalanced(const AVLNode *node){
assert(node != nullptr); // should not be called otherwise
int lh = leftHeight(node);
int rh = rightHeight(node);
if (lh > rh + 1) return false;
if (rh > lh + 1) return false;
return true;
}
// checks calculated heights values
static bool checkHeightNode(const AVLNode *node){
if (node == nullptr) return true; // no stale height on empty tree
if(!checkHeightNode(node->left())) return false; // failure left
if(!checkHeightNode(node->right())) return false; // failure right
int lh = leftHeight(node);
int rh = rightHeight(node);
int max = (lh > rh) ? lh : rh;
return (node->height() == (1 + max));
}
int Solution::countNodes(TreeNode* root)
{
int nodesNum;
int lHeight = leftHeight(root);
int rHeight = rightHeight(root);
if(lHeight == rHeight)
{
nodesNum = (1 << lHeight) - 1;
}
else
{
nodesNum = countNodes(root->left) + countNodes(root->right) + 1;
}
return nodesNum;
}
// restores AVL property when node is left-heavy
static AVLNode* leftRebalanceNode(AVLNode *node){
assert(node != nullptr); // should not be called otherwise
AVLNode *left = node->left();
assert(left != nullptr); // should not be called otherwise
if(rightHeight(left) > leftHeight(left)){ // more rebalancing needed
AVLNode *temp = leftRotateNode(left);
node->setLeft(temp); // new left child for node
temp->setParent(node); // corresponding parent link
updateHeight(node); // re-calc height after change of child
}
return rightRotateNode(node);
}
