gistfile1.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
'''
Solving best-before problem
http://www.spotify.com/se/jobs/tech/best-before/
'''


# ############################################################################


from sys import stdin
from itertools import permutations
from datetime import date


# ############################################################################


def process_line(line):
    digits = [
        int(chunk.strip())
        for chunk in line.split('/')
    ]
    if len(digits) != 3 or any(dig < 0 for dig in digits):
        raise ValueError

    variants = (
        process_variant(*variant)
        for variant in permutations(digits)
    )
    variants = (variant for variant in variants if variant is not None)

    return min(variants).isoformat()


def process_variant(day, month, year):
    if year < 1000:
        year += 2000

    try:
        return date(year, month, day)
    except:
        return None


if __name__ == '__main__':
    for line in (l.rstrip() for l in stdin):
        try:
            print process_line(line)
        except (AttributeError, ValueError):
            print line + ' is illegal'