level_order.py

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

def levelOrderWrong1(root):
    curr_level = [root]
    levels = []

    while root and curr_level:
        levels.append([node.val for node in curr_level])
        curr_level = [n for n in (node.left, node.right) for node in curr_level if n]

    return levels

def levelOrderWrong2(root):
    curr_level = [root]
    levels = []

    while root and curr_level:
        levels.append([node.val for node in curr_level])
        curr_level = [n for n in (node.left, node.right) if n for node in curr_level]

    return levels

def levelOrderRight(root):
    curr_level = [root]
    levels = []

    while root and curr_level:
        
        levels.append([node.val for node in curr_level])
        temp = []
        for node in curr_level:
            for n in (node.left, node.right):
                if n:
                    temp.append(n)

        curr_level = temp

    return levels

root = Node(3, Node(9), Node(20, Node(15), Node(7)))

print(levelOrderWrong1(root))
print(levelOrderWrong2(root))
print(levelOrderRight(root))