C++ AVL tree recalculate height - c++

Question

im working on an implimentation of an AVL tree, and im having problems with my recalculate height function. When i call it i pass in the root of the tree and a variable that has a value of 1. ive stepped through it, and found that once it gets to the while loop it preforms as expected but after that it returns to just ones. can you please look at it and see what i am doing wrong. I will post more code if neede, but i think just the function will provide you with enough information. Thanks
void BinaryTree::recalculate(Node *leaf, int count)
{
if(leaf == NULL)//if we are at the root
{
return;//exit the function
}
if((leaf->getLeft() != NULL))//if we are not at the end of the subtree
{
recalculate(leaf->getLeft(), count);//advance to the next node and re-enter the function
}
if(leaf->getRight() != NULL)//if we are not at the end of the right subtree
{
recalculate(leaf->getRight(), count);//advance to the next node and re-enter the program
}
else
{
while(leaf->getParent() != NULL)//calculate each subtree until we are at the root
{
leaf = leaf->getParent();//get the parent node
count++;//increment the height
if(leaf->getLeft() != NULL)//if there is an item in the left
{
leaf->getLeft()->setHeight(count-1);//sets the hight of the left child
}
if(leaf->getRight() != NULL)//if there is an item in the right
{
leaf->getRight()->setHeight(count -1);//sets the height of the right child
}
}
return;//exit the function
}
}

Answer 1

Your function is supposed to compute the height of each subtree of a binary tree, and save that value in the root node of that subtree. You chose to follow a recursive approach, which is the standard one. In this approach, the height of both left and right subtree must be computed first, and then the highest of both is taken for the current node.
In your implementation, you use a value named count passed in parameter to the recursive call. What is the purpose of that value, given that we need to retrieve a count from subnodes, not pass one to them?
If you:
remove that value from the recalculate parameters
have the recalculate method call itself first on both children if applicable
make the recalculate update the current node height from each subnode height
you should have it working. The following is a possible implementation based on this algorithm:
void BinaryTree::recalculate(Node *leaf) {
int count = 0;
if (leaf == NULL) {
return;
}
if (leaf->getLeft() == NULL && leaf->getRight() == NULL) {
// no child, the height is 0
setHeight(0);
return;
}
if (leaf->getLeft() != NULL) {
recalculate(leaf->getLeft());
count = leaf->getLeft()->getHeight();
}
if (leaf->getRight() != NULL){
recalculate(leaf->getRight());
count = max(count, leaf->getRight()->getHeight());
}
// include leaf in the height
setHeight(count+1);
}
If the getHeight method cannot be used, you may replace it by having recalculate return the height it computed.