Arithmetic Puzzle

arithmetic.py

# problem: http://club.filltong.net/codingdojo/29104
# solved: https://gist.github.com/946455
# coded by jong10

import unittest

def inserted(s, i, c):
    return s[:i] + c + s[i:]

def moved(s):
    return sorted(set(inserted(s[:w] + s[w+1:], i, s[w]) for i in xrange(len(s)) for w in xrange(len(s))))

def isfit(expr):
    try:
        return apply(lambda x, y: x == y, map(eval, expr.split('=')))
    except SyntaxError:
        return False

def solve(s):
    return filter(isfit, moved(s))

class TestArithmetic(unittest.TestCase):
    def test_moved(self):
        self.assertEqual(moved('01'), ['01', '10'])
        self.assertEqual(moved('012'), ['012', '021', '102', '120', '201'])
    def test_isfit(self):
        self.assertEqual(isfit('1+1=2'), True)
        self.assertEqual(isfit('1+2=2'), False)
        self.assertEqual(isfit('1+23='), False)
    def test_solve(self):
        self.assertEqual(solve('6+22=64'), ['62+2=64'])
        self.assertEqual(solve('4*23=72'), ['24*3=72'])
        self.assertEqual(solve('73+3=40'), ['3+37=40', '37+3=40', '7+33=40'])
        self.assertEqual(solve('19-90=1'), ['19-0=19', '19-9=10', '91-90=1'])
        self.assertEqual(solve('3+3=418'), ['3+38=41', '38+3=41'])
        self.assertEqual(solve('8/8=64'), ['48/8=6'])
        self.assertEqual(solve('-12-38=26'), ['12-38=-26'])

if __name__ == '__main__':
    unittest.main()