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solve alphametic puzzles in just 9 lines of code

Yingjie Lan lanyjie at yahoo.com
Sat Sep 25 09:59:47 EDT 2010 
Hi, 

I am teaching Python this semester and
as I am trying to explain the code by
Raymond Hettinger, I need to make it
simpler (this is an introductory course).
And it ends up to be just 9 lines of code.

Just for fun. See also:

http://diveintopython3.org/advanced-iterators.html


Regards,
Yingjie

############Code starts here###########

import itertools
def solve(puzzle):
    "solve alphametic puzzles in just 9 lines of code."
    words = [w for w in puzzle.split() if w.isalpha()]
    nonzeros = {w[0] for w in words}
    others = {a for a in ''.join(words) if a not in nonzeros}
    chars = [ord(c) for c in nonzeros]+[ord(c) for c in others]
    assert len(chars) <= 10, 'Too many letters'
    for guess in itertools.permutations('0123456789', len(chars)):
        if '0' not in guess[:len(nonzeros)]:
            equation = puzzle.translate(dict(zip(chars, guess)))
            if eval(equation): return equation
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