BST to sorted DLL

7.cpp

// Converting bst to sorted DLL
// go in in order and and keep track of previous node and make it previous to current node and current node next to this node.
void bsttodll(node *root, node **head){
  if(root == NULL) return ;
  static node *prev = NULL;
  bsttodll(root->left, head);
  if(prev == NULL) *head = root;
  else {
    root -> previous = prev;
    prev -> next = previous;
  }
  bsttodll(root->right, head);
}