算法竞赛中用于解决卡常问题

int rd(){
    int k = 0;
    char c = getchar();
    while(!isdigit(c)){
        c = getchar();
    }
    while(isdigit(c)){
        k= (k << 1) + (k << 3) + (c^'0'), c = getchar();
    }
    return k;
}

void wr(int x)
{
    if (x > 9)
        wr(x / 10);
    putchar((x % 10) ^ '0');
}

用法：
假如读取(int) a
int a = rd();