值班轮换把负担分得均匀

from collections import Counter
from datetime import date, timedelta

TEAM = ["ana", "ben", "cara", "dev", "elin"]
START = date(2027, 8, 2)  # a Monday
WEEKS = 22
HOLIDAYS = {date(2027, 8, 9), date(2027, 8, 30)}  # Monday public holidays

rota = []  # list of (monday, person or None)
cursor = 0
for week in range(WEEKS):
    monday = START + timedelta(weeks=week)
    if monday in HOLIDAYS:
        rota.append((monday, None))  # holiday week: nobody on call, pointer stays
        continue
    person = TEAM[cursor % len(TEAM)]
    rota.append((monday, person))
    cursor += 1

assigned = [person for _, person in rota if person is not None]
counts = Counter(assigned)

for monday, person in rota:
    label = person if person else "holiday-skip"
    print(f"{monday.isoformat()} -> {label}")
print("counts:", dict(sorted(counts.items())))

# Load-balance statistics: 20 assigned weeks / 5 people = 4 each.
assert len(assigned) == WEEKS - len(HOLIDAYS) == 20, len(assigned)
assert set(counts) == set(TEAM), counts
assert all(count == 4 for count in counts.values()), dict(counts)
assert max(counts.values()) - min(counts.values()) == 0, dict(counts)
# Holiday weeks consume no turn and hold nobody.
assert all(monday not in HOLIDAYS for monday, person in rota if person is not None)
assert sum(1 for _, person in rota if person is None) == len(HOLIDAYS)
# Nobody works two calendar turns in a row (pointer only advances on assigned weeks).
for prev, current in zip(assigned, assigned[1:]):
    assert prev != current, (prev, current)
print("PASS: 20 on-call weeks across 5 people, 4 each, holidays skipped, no back-to-back")