template <class T> void read(T& x)
{
char ch = gc(); x = 0; bool f = 1;
while (!(‘0‘ <= ch && ch <= ‘9‘) && ch != ‘-‘) ch = gc();
if (ch == ‘-‘) f = 0, ch = gc();
while (‘0‘ <= ch && ch <= ‘9‘) x = (x << 1) + (x << 3) + ch - ‘0‘, ch = gc();
if (!f) x = -x;
}
原文：https://www.cnblogs.com/mayouyou/p/9463970.html