### Python program to convert a binary tree into doubly linked list in spiral fashion.

Description:
Given a Binary Tree, convert it into Doubly Linked List where the nodes are represented Spirally. The left pointer of the binary tree node should act as a previous node for created DLL and right pointer should act as next node.

Program:

class newNode: def __init__(self, data): self.data = data self.left = None self.right = None def push(head_ref, node): node.right = (head_ref) node.left = None if ((head_ref) != None): (head_ref).left = node (head_ref) = node def printList(node): i = 0 while (i < len(node)): print(node[i].data, end = " ") i += 1 def spiralLevelOrder(root): if (root == None): return q = [] q.append(root) stk = [] level = 0 while (len(q)): nodeCount = len(q) # Dequeue all Nodes of current level # and Enqueue all Nodes of next level if (level&1): # odd level while (nodeCount > 0): # dequeue node from front & # push it to stack node = q[0] q.pop(0) stk.append(node) # insert its left and right children # in the back of the deque if (node.left != None): q.append(node.left) if (node.right != None): q.append(node.right) nodeCount -= 1 else: # even level while (nodeCount > 0): # dequeue node from the back & # push it to stack node = q[-1] q.pop(-1) stk.append(node) # inserts its right and left # children in the front of # the deque if (node.right != None): q.insert(0, node.right) if (node.left != None): q.insert(0, node.left) nodeCount -= 1 level += 1 # head pointer for DLL head = [] while (len(stk)): head.append(stk[0]) stk.pop(0) print("Created DLL is:") printList(head) # Driver Code if __name__ == '__main__': root = newNode(1) root.left = newNode(2) root.right = newNode(3) root.left.left = newNode(4) root.left.right = newNode(5) root.right.left = newNode(6) root.right.right = newNode(7) root.left.left.left = newNode(8) root.left.left.right = newNode(9) root.left.right.left = newNode(10) root.left.right.right = newNode(11) root.right.left.right = newNode(13) root.right.right.left = newNode(14) spiralLevelOrder(root)

Output:
Created DLL is:
1 2 3 7 6 5 4 8 9 10 11 13 14
>>>

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