Python: Solve GLAT question 1

GLAT-1.py

#!/usr/bin/env python
"""
A brute-force approach to solve the first quesiton of GLAT
More about GLAT: http://googleblog.blogspot.de/2004/09/pencils-down-people.html

The question is as follows:


1. Solve this cryptic equation, realizing of course that values for M and E
   could be interchanged. No leading zeros are allowed.

WWWDOT - GOOGLE = DOTCOM


The current solution ignores the hint. Well, it ignores pretty much everything.
"""
import itertools
import sys


chars = [list(word) for word in "WWWDOT,GOOGLE,DOTCOM".lower().split(',')]
uchars = set(itertools.chain(*chars))
uchars.add('')

permutations = itertools.permutations(uchars, 10)
equations = [list(reversed(c)) for c in reversed(zip(*chars))]


def map_(per, equations):
    o3 = 0
    for op1, op2, su in equations:
        o1, o2, s = per.index(op1), per.index(op2), per.index(su)

        if not (o1 + o2 + o3) % 10 == s:
            return False
        o3 = (o1 + o2 + o3) / 10

    return True


def reduce_(iterable, equations):
    for per in iterable:
        if map_(per, equations):
            return per
    return False

exitcode = 1

sol = reduce_(permutations, equations)
if sol:
    exitcode = 0
    for i, p in enumerate(sol):
        if p:
            print "{0}: {1}".format(p.upper(), i)

if exitcode:
    print "boohoo!"

sys.exit(exitcode)