门家族与半加器:XOR/AND 的可逆实现

1. 输入 a=1、b=1:s = 1⊕1 = 0;c = 1∧1 = 1

2. 核对恒等式:a+b = 2·1+0 = 2 = 10₂ ✓

3. 计数键按"c[0] 在最右"读:c₃c₂c₁c₀ = 1011₂ = 11 ✓

类型code-walkthrough + 命题框/演算