Question

I have a MySQL database and I am storing user records in the table structure below

User_mst
-------------------
id
user_name
parent_id
left_id
right_id
position       (keyword "left", "right" as string)
node_level

I am storing user records in a binary tree structure, so that it means there is a maximum of 2 child nodes under each node (User).

From this structure, I want to create a function which has

Input:

1.user_id
2.level
3.position

And the Output should be :

Number of Nodes under given user_id on given level and on given position.

So e.g. if the function is like that below

get_nodes(3, 4, 'left');

Then it should return:
There are X number of nodes under User ID 3 on Level 4

I think that I have to build a function that will process recursively though I would like suggestions.

Please help me build this function. Use any programming language such as C, PHP etc.
I am just looking for the logic here.

Here is the SQL for Create Table and some sample Insert statements:

http://paste.ubuntu.com/1218345/

Thanks in advance

Answer 1

if you are just looking for the logic, then pseudo-C-code should be fine:

struct NodeStructure
{
  int ID;
  int leftID;
  int rightID;
  int level;
  ...
};

int countChildren( int nodeID, int level )
{
  NodeStructure * node = find( nodeID );

  if( node == NULL )
    return 0;

  if( node.level == level )
    return 1;

  return countChildren( x.leftID, level ) + countChildren( x.rightID, level );

}

NodeStructure * find( int nodeID )
{
  // SQL CODE:
  // SELECT * FROM User_mst WHERE id = nodeID;

  // if( /* node has been found */ )
    // fill NodeStructure
  // else
    // return NULL;
}