類比二進位實現減法

#! /usr/bin/python# coding=utf-8import mathdef main(x,y):    #對減數取反    x, y = bin(x)[2:], bin(y)[2:]    l = max([len(x),len(y)]) #最大長度    #對y取反    y = "1" * (l - len(y)) + "".join(['1' if i == '0' else '0' for i in y])    x,y = int(x,2), int(y,2)    z = x + y + 1    z = bin(z)    #拿掉最高位    z = z[3:]    return int(z,2)        if __name__ == '__main__':    import unittest,random    class cacheTest(unittest.TestCase):        def test_img(self):            for i in range(0,100000):                x, y = random.randint(1, 1000),random.randint(1, 1000)                if x < y : x,y = y,x                self.assertEqual(main(x, y), x - y)    unittest.main()