Sunday Times Teaser 2526

by H Bradley and C Higgins

Published: 20 February 2011 (link)

Orla was married in this century, on her lucky day of the week, and her twin sister Enya’s lucky-number day of the month. Enya told Orla on that big day that she intended her own wedding to be on the same lucky day of the week and lucky-number day of the month. She realised that it could not be in the same year as Orla’s, but Orla added that Enya could not be married in the following year, either. Enya married months later, the actual number of months being the sum of the six digits of Orla’s wedding date.

What was Orla’s wedding date?

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Brian Gladman permalink


from datetime import date, timedelta
from calendar import monthrange

# Orla's wedding is this century (set to
# last date of previous to allow for the
# increment)
orla = date(day=31, month=12, year=1999)

# Orla's wedding had occured before the date
# that the puzzle was published
while orla < date(day=11, month=2, year=2011):
  orla += timedelta(days=1)
  
  # the sum of the digits in Orla's date
  sum_digits = sum(map(int, str(orla.day) 
          + str(orla.month) + str(orla.year % 100)))
  
  # now consider Enya's wedding date
  enya_month, enya_year = orla.month, orla.year
  
  # which is after Orla's by not more than a number
  # of months equal to the Orla's date's digit sum
  for months in range(1, sum_digits + 1):
    
    # advance enya's date a month at a time, looking
    # for a day of the month AND a day of the week 
    # that match Orla's
    enya_year = enya_year + (1 if enya_month == 12 else 0) 
    enya_month = (enya_month % 12) + 1
    
    # we only need to consider months in which Orla and
    # Enya's day of the month is valid
    if orla.day <= monthrange(enya_year, enya_month)[1]:
      enya = date(day=orla.day, month=enya_month, year=enya_year)
      
      # check for a weekday match
      if enya.weekday() == orla.weekday():
        # the first match for both the day of the month and 
        # the weekday cannot occur in Orla's wedding year
        # or in the year after
        if enya_year < orla.year + 2 or months != sum_digits:
          break
        print("Orla married on {} (Enya married in {}).".
          format(orla.strftime("%A %d %B %Y"), enya.strftime("%B %Y")))

from datetime import date, timedelta

from calendar import monthrange

# Orla's wedding is this century (set to

# last date of previous to allow for the

# increment)

orla = date(day=31, month=12, year=1999)

# Orla's wedding had occured before the date

# that the puzzle was published

while orla < date(day=11, month=2, year=2011):

orla += timedelta(days=1)

# the sum of the digits in Orla's date

sum_digits = sum(map(int, str(orla.day)

+ str(orla.month) + str(orla.year % 100)))

# now consider Enya's wedding date

enya_month, enya_year = orla.month, orla.year

# which is after Orla's by not more than a number

# of months equal to the Orla's date's digit sum

for months in range(1, sum_digits + 1):

# advance enya's date a month at a time, looking

# for a day of the month AND a day of the week

# that match Orla's

enya_year = enya_year + (1 if enya_month == 12 else 0)

enya_month = (enya_month % 12) + 1

# we only need to consider months in which Orla and

# Enya's day of the month is valid

if orla.day <= monthrange(enya_year, enya_month)[1]:

enya = date(day=orla.day, month=enya_month, year=enya_year)

# check for a weekday match

if enya.weekday() == orla.weekday():

# the first match for both the day of the month and

# the weekday cannot occur in Orla's wedding year

# or in the year after

if enya_year < orla.year + 2 or months != sum_digits:

break

print("Orla married on {} (Enya married in {}).".

format(orla.strftime("%A %d %B %Y"), enya.strftime("%B %Y")))

Sunday Times Teaser 2526

by H Bradley and C Higgins

Published: 20 February 2011 (link)

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