it all depends on the traversal. If you are using -1, code would be

if(head==NULL)
    return -1;
int leftcount= 1+height(root->left);

now, if you want to use 0 then, code would be

  if(head==NULL)
    return 0;
if(root->left!=NULL)
    int leftcount= 1+height(root->left);