一.操作符的分类
二.二进制和进制转换
cpp
int main()
{
int a = 0177;
printf("%d\n", a);//以10进制的形式打印有符号的整数
int b = 0x17;
printf("%d\n", b);
return 0;
}
//%x - 16进制形式打印
//%o - 8进制的形式打印
1. 2进制转10进制
2. 10进制转2进制
3. 2进制转8进制和16进制
三.原码、反码、补码
cpp
#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int main()
{
int num = 10;//signed int num = 10;
//10是存放在整型变量num中，占4个字节 == 32bit位
//00000000000000000000000000001010 - 原码
//00000000000000000000000000001010 - 反码
//00000000000000000000000000001010 - 补码
int num2 = -10;
//-10是存放在整型变量num2中，占4个字节 == 32bit位
//10000000000000000000000000001010 - 原码
//11111111111111111111111111110101 - 反码
//11111111111111111111111111110110 - 补码
return 0;
}补码的好处:
cpp
1-1
1+(-1)
00000000000000000000000000000001 ---> 1的原码
10000000000000000000000000000001 ---> -1的原码
10000000000000000000000000000010 -> -2
使用补码就可以
00000000000000000000000000000001 ---> 1的补码
10000000000000000000000000000001
11111111111111111111111111111110
11111111111111111111111111111111 ----> -1的补码
00000000000000000000000000000001
00000000000000000000000000000000 ---> 0
四.移位操作符
cpp
int main()
{
int m = 10;
int n = m << 1;
printf("n = %d\n", n);
printf("m = %d\n", m);
return 0;
}
m是不会发送变化的,n是m << 1的值
cpp
int main()
{
int m = 10;
int n = m >> 1;
printf("n = %d\n", n);
printf("m = %d\n", m);
return 0;
}
cpp
int main()
{
int m = -10;
int n = m >> 1;
//10000000000000000000000000001010
//11111111111111111111111111110101
//11111111111111111111111111110110
//n = m>>1
//11111111111111111111111111111011
//10000000000000000000000000000100
//10000000000000000000000000000101
//-5
printf("m = %d\n", m);
printf("n = %d\n", n);
return 0;
}
五.位操作符：&、|、^、~
cpp
int main()
{
int a = 3;
int b = -5;
int c = a & b;
//按（2进制）位与
//计算规则：对应的二进制位进行与运算
//只要有0就是0，两个同时为1才是1
//00000000000000000000000000000011 --- 3的补码
//10000000000000000000000000000101 --- -5的原码
//11111111111111111111111111111010 反码
//11111111111111111111111111111011 --- -5的补码
//00000000000000000000000000000011 --- 3的补码
//00000000000000000000000000000011
printf("c = %d\n", c); // 3
return 0;
}
cpp
int main()
{
int a = 3;
int b = -5;
int c = a | b;
//按（2进制）位或
//计算规则：对应的二进制位进行或运算
//只要有1就是1，两个同时为0才是0
//00000000000000000000000000000011 --- 3的补码
//10000000000000000000000000000101 --- -5的原码
//11111111111111111111111111111010 反码
//11111111111111111111111111111011 --- -5的补码
//00000000000000000000000000000011 --- 3的补码
//11111111111111111111111111111011
printf("c = %d\n", c); // -5
return 0;
}
cpp
int main()
{
int a = 3;
int b = -5;
int c = a ^ b;
//按（2进制）位异或
//计算规则：对应的二进制位进行异或运算
//相同为0，相异为1
//00000000000000000000000000000011 --- 3的补码
//10000000000000000000000000000101 --- -5的原码
//11111111111111111111111111111010 反码
//11111111111111111111111111111011 --- -5的补码
//00000000000000000000000000000011 --- 3的补码
//11111111111111111111111111111000
//10000000000000000000000000000111
//10000000000000000000000000001000
printf("c = %d\n", c); // -8
return 0;
}
cpp
//~ - 按位取反
int main()
{
int a = 1;
int b = ~a;
//00000000000000000000000000000001 -- 1的补码
//11111111111111111111111111111110（补码）
//10000000000000000000000000000001
//10000000000000000000000000000010 > -2
printf("%d\n", b); // -2
return 0;
}
cpp
int main()
{
int a = 0;
//00000000000000000000000000000000
//11111111111111111111111111111111
//10000000000000000000000000000000
//10000000000000000000000000000001 -1
int b = ~a; // -1
printf("%d\n", b);
return 0;
}
cpp
int main()
{
int a = 3;
int b = 5;
//交换a和b的值
printf("a=%d b=%d\n", a, b);
//int c = a;
//a = b;
//b = c;
//a = a + b;
//b = a - b;
//a = a - b;
//这种写法的缺陷是：a和b如果非常大，求和后的结果超过了整型的最大值
a = a ^ b;
b = a ^ b;
a = a ^ b;
printf("a=%d b=%d\n", a, b);
return 0;
}
cpp
//异或操作符的特点：
//a^a = 0
//0^a = a
//
//3^3^5 = 5
//3^5^3 = 5
//
//011
//101
//110
//011
//101
cpp
int main()
{
int a = 0;
scanf("%d",&a);
int i = 0;
int count = 0;
for (i = 0; i < 32; i++)
{
if (((a >> i) & 1) == 1)
count++;
}
printf("%d\n", count);
return 0;
}
-1就有32个1
什么时候需要考虑正负数呢？
cpp
int count_one_bit(unsigned int n)
{
int count = 0;
while (n)
{
if (n % 2 == 1)
count++;
n = n / 2;
}
return count;
}
int main()
{
int num = 0;
scanf("%d", &num);
//求一个整数存储在内存中的二进制中1的个数
int n = count_one_bit(num);
printf("%d\n", n);
return 0;
}
cpp
int count_one_bit(int n)
{
int count = 0;
while (n)
{
n = n & (n - 1);
count++;
}
return count;
}
int main()
{
int num = 0;
scanf("%d", &num);
//求一个整数存储在内存中的二进制中1的个数
int n = count_one_bit(num);
printf("%d\n", n);
return 0;
}
cpp
n = n&(n-1)
效果：把n的二进制中最右边的1去掉了
n=15
1111 - n
1110 - n-1
1110 - n
1101 - n-1
1100 - n
1011 - n-1
1000 - n
0111 - n-1
0000 - n
cpp
//判断一个数n是否是2的次方数
int main()
{
int n = 0;
scanf("%d", &n);
if ((n & (n - 1)) == 0)
{
printf("Yes\n");
}
else
{
printf("No\n");
}
return 0;
}
cpp
int main()
{
int n = 13;
n = n | (1 << 4);
printf("%d\n", n);
n = n & ~(1 << 4);
printf("%d\n", n);
return 0;
}六.单目操作符
七.逗号表达式
cpp
int main()
{
int a = 1;
int b = 2;
int c = (a > b, a = b + 10, a, b = a + 1);//逗号表达式
printf("%d\n", c); // 13
return 0;
}八.下标访问[]、函数调用()
cpp
int Add(int x, int y)
{
return x + y;
}
void test()
{
printf("hehe\n");
}
int main()
{
//int arr[10] = { 0 };
//arr[5] = 6;//[] - 下标引用操作符
// arr 和 5是两个操作数
int c = Add(3, 5);//()函数调用操作符 - 函数名和参数就是操作数
test();//()函数调用操作符
printf("hehe\n");
return 0;
}
cpp
//sizeof是操作符，不是函数
int main()
{
int a = 10;
printf("%zd\n", sizeof(a));
printf("%zd\n", sizeof a);
return 0;
}