1.

int read()
{
    char c = getchar();
    int f = 1, x = 0;
    while(!isdigit(c)) {if(c == '-') f = -1;c = getchar();}
    while(isdigit(c)){x = x * 10 + c - 48;c = getchar();}
    //对于“x” 还可以- x = (x << 1) + (x << 3) + (c - 48); 
    //"48"指 ‘0’；
    return x * f;
}

isdigit() 算机C(C++)语言中的一个函数，主要用于检查其参数是否为十进制数字字符

int read()
{
    char c = getchar();
    int f = 1, x = 0;
    while(c<'0'||c>'9') {if(c == '-') f = -1;c = getchar();}
    while(c>='0'&&c<='9'){x = x * 10 + c - 48;c = getchar();}
    return x * f;
}

注：要写<cstring>头