task.py

#https://www.hackerrank.com/challenges/swap-nodes-algo
class Node:
    def __init__(self,data, level=1): 
        self.data = data  
        self.left = None  
        self.right = None 
        self.level = level

root = Node(1)
n = int(input())
q = [root]
for _ in range(n):
    l, r = tuple(map(int, input().split()))
    if l != -1:
        node = Node(l, q[0].level+1)
        q[0].left = node
        q.append(node)
    if r != -1:
        node = Node(r, q[0].level+1)
        q[0].right = node
        q.append(node)
    del q[0]
    
def prtr(node):
    s = [[0, node]]
    while s:
        step, n = s[-1]
        s[-1][0] += 1
        if step > 1 or not n:
            del s[-1]
        elif step == 0:
            s.append([0, n.left])
        else:
            print(n.data, end=' ')
            s.append([0, n.right])
    print()
    
def swap(node, level):
    q = [node]
    while q:
        if q[0].level % level == 0:
            t = q[0].left
            q[0].left = q[0].right
            q[0].right = t
        if q[0].left:
            q.append(q[0].left)
        if q[0].right:
            q.append(q[0].right)
        del q[0]   

n = int(input())

for _ in range(n):
    lvl = int(input())
    swap(root, lvl)
    prtr(root)