import unittest
################################################################################
# Implementation
################################################################################
def is_first_come_first_served(to, di, xs):
# All the guards, assertions we should need.
if to == di == xs == []:
return True
elif to == di == []:
return False
elif to == []:
return di == xs
elif to == []:
return di == xs
elif di == []:
return to == xs
elif xs == []:
return False
elif len(xs) != (len(to) + len(di)):
return False
fst, snd = to, di
if xs[0] == to[0]:
fst, snd = to, di
elif xs[0] == di[0]:
fst, snd = di, to
else:
return False
fst_done, snd_done = False, False
fi, si = 1, 0
for i in range(1, len(xs)):
# Short-circuit and avoid index-out-of-bounds without introducing overly
# defensive, sloppy code.
if fst_done:
return snd[si:] == xs[i:]
elif snd_done:
return fst[fi:] == xs[i:]
if fst[fi] == xs[i]:
fi += 1
elif snd[si] == xs[i]:
si += 1
else:
return False
fst_done, snd_done = fi == len(fst), si == len(snd)
return True
################################################################################
# Tests
################################################################################
class Test(unittest.TestCase):
def test_both_registers_have_same_number_of_orders(self):
result = is_first_come_first_served([1, 4, 5], [2, 3, 6],
[1, 2, 3, 4, 5, 6])
self.assertTrue(result)
def test_registers_have_different_lengths(self):
result = is_first_come_first_served([1, 5], [2, 3, 6], [1, 2, 6, 3, 5])
self.assertFalse(result)
def test_one_register_is_empty(self):
result = is_first_come_first_served([], [2, 3, 6], [2, 3, 6])
self.assertTrue(result)
def test_served_orders_is_missing_orders(self):
result = is_first_come_first_served([1, 5], [2, 3, 6], [1, 6, 3, 5])
self.assertFalse(result)
def test_served_orders_has_extra_orders(self):
result = is_first_come_first_served([1, 5], [2, 3, 6],
[1, 2, 3, 5, 6, 8])
self.assertFalse(result)
def test_one_register_has_extra_orders(self):
result = is_first_come_first_served([1, 9], [7, 8], [1, 7, 8])
self.assertFalse(result)
def test_one_register_has_unserved_orders(self):
result = is_first_come_first_served([55, 9], [7, 8], [1, 7, 8, 9])
self.assertFalse(result)
unittest.main(verbosity=2)
