原理就是getchar()
比scanf快,所以先以字符读入,再转换为整数
inline int read() //整数快读
{
int x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9')
{
if (ch == '-')
f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9')
{
x = (x << 1) + (x << 3) + (ch ^ 48);
//(x << 1) + (x << 3) = x * 2 + x * 8 = x * 10
ch = getchar();
}
return x * f;
}