def _traversal(node, depth):
    if (node != None):
        _larger(depth)
        tmp = ans[depth]
        tmp.append(node.val)
        _traversal(node.left, (depth + 1))
        _traversal(node.right, (depth + 1))
def _traversal(node, depth):
    if (node != None):
        _larger(depth)
        tmp = ans[depth]
        tmp.append(node.val)
        _traversal(node.left, (depth + 1))
        _traversal(node.right, (depth + 1))