Write a C program to determine the number of elements (or size) in a tree.

Try this C program

int tree_size(struct node* node) 

{ 

  if (node==NULL) 

  { 

    return(0); 

  } 

  else 

  { 

    return(tree_size(node->left) + tree_size(node->right) + 1); 

  } 

}