430. Flatten a Multilevel Doubly Linked List - LeetCode Solution

"""
# Definition for a Node.
class Node:
    def __init__(self, val, prev, next, child):
        self.val = val
        self.prev = prev
        self.next = next
        self.child = child
"""

class Solution:
    def trav(self,head1):
        root = head1
        if not root:
            return None
        while root:
            a = None
            if root.child:
                a = self.trav(root.child) 
            if a:
               
                a.prev = head1
                
                temp = root.next
               
                root.next = a
                while root.next:
                    root = root.next
                
                root.next = temp

            root = root.next
        return head1
                
                
    def flatten(self, head: 'Node') -> 'Node':
        if not head:
            return None
        
        
        root = self.trav(head)
        temp = root
        temp.prev = None
        temp.child= None
        last = temp
        temp = temp.next
        while temp:
            temp.child = None
            temp.prev = last
            last = temp
            temp = temp.next
            
        
        return root