# vacation.py - Find out when two people can take a vacation during some
# 31-day month, based on their vacation schedules.
# This program illustrates how to use a bit vector to store a "set" of
# information.  An integer consists of bits, and we'll use bits 1-31
# to see which day(s) we can both take off.  
# If a bit = 1, it's available for vacation; 0 means we have to work.

begin = int(input("Starting date of your vacation (1-31):  "))
end = int(input("Ending date of your vacation (1-31):  "))

# For each day in the range the user listed, turn on the appropriate bit.
userVacation = 0
for day in range(begin, end+1):
    userVacation |= 1 << day

# Repeat procedure for a friend.
begin = int(input("Starting date of friend's vacation (1-31):  "))
end = int(input("Ending date of friend's vacation (1-31):  "))

friendVacation = 0
for day in range(begin, end+1):
    friendVacation |= 1 << day

# -------------------------------------------------------------------
# Print out when our 2 vacations are.
print("\nHere is when you can days off.  Y = you, F = friend")
print("         1111111111222222222233")
print("1234567890123456789012345678901")
for day in range(1, 32):
    if userVacation & (1 << day) != 0:
        print("Y", end = "")
    else:
        print(" ", end = "")
print(" your vacation days")

for day in range(1, 32):
    if friendVacation & (1 << day) != 0:
        print("Y", end = "")
    else:
        print(" ", end = "")
print(" friend's vacation days\n")

# -------------------------------------------------------------------
# Now check for overlap.  We use '&' for the intersection of 2 sets.
combinedVacation = userVacation & friendVacation

if combinedVacation == 0:
    print("Sorry, your vacation dates don't overlap.\n")
else:
    print("Here is when your vacation dates overlap:")
    for day in range(1, 32):
        if combinedVacation & (1 << day) != 0:
            print(day, end = " ")
    print("\n")

# -------------------------------------------------------------------
# Let's say your friend is someone you'd rather not hang around with
# on your time off.  You want to be sure to take your vacation when
# your friend has to work.
userAlone = userVacation & ~ friendVacation

if userAlone == 0:
    print("Sorry, you can't take a vacation while your friend is working.\n")
else:
    print("Here's when you can take a vacation by yourself:")
    for day in range(1, 32):
        if userAlone & (1 << day) != 0:
            print(day, end = " ")
    print("\n")