Question

请问C语言中 !(a||b) 和！a&&！b 等价吗？

Answer 1

答案是：等价
证明如下：
1. a = 0, b = 0时, a || b == 0, !(a || b) == 1, !a && !b == 1
2. a = 0, b = 1时, a || b == 1, !(a || b) == 0, !a && !b == 0
3. a = 1, b = 0时, 和2相同
4. a = 1, b = 1时, a || b == 1, !(a || b) == 0, !a && !b == 0

用代码证明如下：
#include <stdio.h>

int main()
{
int a, b;

a = 0, b = 0;
if ((!(a || b)) == (!a && !b)) printf("Equal.\n");

a = 1, b = 0;
if ((!(a || b)) == (!a && !b)) printf("Equal.\n");

a = 0, b = 1;
if ((!(a || b)) == (!a && !b)) printf("Equal.\n");

a = 1, b = 1;
if ((!(a || b)) == (!a && !b)) printf("Equal.\n");

return 0;
}

输出结果如下：
Equal.
Equal.
Equal.
Equal.

Answer 2

等价

a b !(a||b) ！a&&！b
0 0 1 1
0 1 0 0
1 0 0 0
1 1 0 0