只使用指向二叉树的根的一个指针T，计算T中节点的个数，T中树叶的片数，T中满节点的个数

int countNodes(AvlTree t) {
if (t == NULL)
return 0;
return countNodes(t->left) + countNodes(t->right) + 1;
}

int countLeaves(AvlTree t) {
if (t == NULL)
return 0;
else if (t->left == NULL&&t->right == NULL)
return  1;
else
return countLeaves(t->left) + countLeaves(t->right);
}

int countFull(AvlTree t) {
if (t == NULL)
return 0;
else if (t->left &&t->right)
return   countFull(t->left) + countFull(t->right) + 1;
else
return countFull(t->left) + countFull(t->right);
}