How to convert a binary search tree into a doubly linked list?

Question

Given a binary search tree, i need to convert it into a doubly linked list(by traversing in zig zag order) using only pointers to structures in C++ as follows,

Given Tree:

                1
                |
        +-------+---------+
        |                 |
        2                 3
        |                 |
   +----+---+        +----+---+
   |        |        |        |
   4        5        6        7
   |        |        |        |
+--+--+  +--+--+  +--+--+  +--+--+
|     |  |     |  |     |  |     |
8     9  10    11 12    13 14    15

Node Structure:

struct node
{
    char * data;
    node * left;
    node * right;
};

Create List(zig zag order):

1 <-> 3 <-> 2 <-> 4 <-> 5 <-> 6 <-> 7 <-> 15 <-> ... <-> 8

Could someone please help me out.

Answer 1

This is a Breadth-first search algorithm. Wikipedia has a good explanation on how to implement it.

After implementing the algorithm, creating your linked list should be a no-brainer (since it will only be a matter of appending each visited element to the list)