Count the number of nodes of a binary tree

 Question: How do you count the nodes of a binary tree?

Solution : 

Like almost all functions in a binary tree, this algorithm also needs a recursive function. 

• The no. of nodes of a binary tree = 0 if the node is NULL
• = 1 +
•  no. of nodes in left sub-tree+
• no.of nodes in right sub-tree.
• Calculate recursively for all sub-trees.

Here is C++ code for the same. 

 int bintree::count()
   {
      return count_leaf_nodes(root);
   } 
  int bintree::count_nodes(node * nd)
  {
    if(nd==NULL)
       return 0;
    if(nd->left ==NULL  && nd->right==NULL)
       return 1;
   return 1+count_nodes(nd->left)+count_nodes(nd->right);
  }