cal max width of a tree

tree_width.py

class Node:
    def __init__(self):
        self.left = None
        self.right = None

def max_width(root):
    if not root:
        return 0
    arr1 = []
    arr2 = []
    arr1.append(root)
    ans = 1
    while len(arr1) > 0:
        arr2 = []
        for node in arr1:
            if node.left:
                arr2.append(node.left)
            if node.right:
                arr2.append(node.right)
        ans = max(ans, len(arr2))
        arr1 = arr2
    return ans

n1 = Node()
n2 = Node()
n3 = Node()
n4 = Node()
n5 = Node()
n6 = Node()
n7 = Node()
n8 = Node()
n9 = Node()
n0 = Node()
n1.left = n2
n1.right = n3
n2.left = n4
n2.right = n5
n4.right = n6
n5.left = n7
n5.right = n8
n3.right = n9
n3.left = n0
print max_width(n1)
print max_width(n2)