# TADM2E 3.22

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For this problem, an easy solution is to do an in order traversal of the binary tree. Instead of printing the node value, push the value into a LIFO queue. When the traversal is done, you can create the linked list by popping the items one after the other while progressively creating the Linked List. This algorithm has a complexity of O(n).

An other solution is to use the rotate clockwise method described link here

Code Snippet. O(n) reusing tree nodes without using additional containers.

<pre> // push a flattened tree to the right of another flattened tree void push_right(node *pN, node *pR) {

 assert(pN->left == NULL);
if(pN->right)


push_right(pN->right, pR);

 else


pN->right = pR; }

// return the head of a linked list composed of flattened nodes // flattened left + pN + flattened right node *flatten(node *pN) {

 node *L = NULL, *R = NULL;
if(pN->left) {


L = flatten(pN->left); pN->left = NULL;

 }
if(pN->right) {


R = flatten(pN->right); pN->right = NULL;

 }
if(L != NULL)


push_right(L, pN);

 else


L = pN;

 if(R != NULL)


push_right(L, R);

 return L;


}

// example output

Printing Tree: 0 (0): 28 --(1): 12

(2): 0
(3): 8
(2): 22

--(1): 84

(2): 40
(3): 34
(3): 64
(2): 89

Flatten ... Printing Tree: 0 (0): 0 --(1): 8

(2): 12
(3): 22
(4): 28
(5): 34
(6): 40
(7): 64
(8): 84
(9): 89

</pre>