异或运算规则

1. 归零律：a ⊕ a = 0
2. 恒等律：a ⊕ 0 = a
3. 交换律：a ⊕ b = b ⊕ a
4. 结合律：a ⊕b ⊕ c = a ⊕ (b ⊕ c) = (a ⊕ b) ⊕ c;
5. 自反：a ⊕ b ⊕ a = b.
6. d = a ⊕ b ⊕ c 可以推出 a = d ⊕ b ⊕ c.