Here in 2nd solution you wrote
l2 = [x for x in range(0, 21) if (x not in l2)] which is wrong.
it should be l2 = [x for x in range(0, 21) if (x not in l1)]
Here in 2nd solution you wrote
l2 = [x for x in range(0, 21) if (x not in l2)] which is wrong.
it should be l2 = [x for x in range(0, 21) if (x not in l1)]