Converting BST to sorted Doubly Linked List

Today, one of my friend asked how to convert a Binary Search Tree to sorted Doubly Linked List. He came across this problem while preparing for interview. I then began to dig what I could remember about BST. I had learnt from my Data Structures course in college that most tree problems boil down to tree traversal problems. So I started thinking along that line and suddenly came out with a solution. The idea is to traverse the tree In Order and adjust the pointers accordingly. The code for this is pretty straight forward.

Node *last_left = 0;

void traverse(Node * node)
{
 if(node == 0)
   return;
 //traverse left tree
 traverse(node->left_);

 //adjust the left and right pointers (left points to previous
//and right points to next)
 //in terms of doubly linked list
 if(last_left != 0){
   last_left->right_ = node;
   node ->left_ = last_left;
   last_left = node;
 }
 else
   last_left = node;

 //traverse right subtree
 traverse(node->right_);
}