Retrieving a Binary-Tree node's depth non-recursively

Question

Can anyone point out a way of getting the depth of a Node in a Binary Tree (not a balanced one, or BST) without using recursion? Ideally in Java/C/C#

The no

Answer 1

Here is the most efficient solution I've come up with (C++). The trick is to use a second queue to store the children of all nodes at your current level. This will work for balanced and unbalanced binary trees.

template 
struct TreeNode {
  TreeNode* left_;
  TreeNode* right_;
  T* data_;
};

template 
int find_depth( const TreeNode* root ) {   
  if ( root == NULL ) return 0;
  int depth = 0;
  std::queue*>* q1 = new std::queue*>;
  std::queue*>* q2 = new std::queue*>;
  q1->push( root );
  while ( !q1->empty() ) {
    // At the top of the outer loop q1 contains a complete horizontal level of the tree                                                                                  
    depth++;

    // Swap the queue pointers to avoid any deep copies                                                                                                                  
    std::queue*>* tmpQ = q2;
    q2 = q1;
    q1 = tmpQ;

    // Iterate over this level, inserting all children into q1                                                                                                           
    while( !q2->empty() ) {
      const TreeNode* node = q2->front();
      if ( node->left_ != NULL ) q1->push( node->left_ );
      if ( node->right_ != NULL ) q1->push( node->right_ );
      q2->pop();
    }
  }
  delete q1;
  delete q2;
  return depth;
}