快速幂&快速乘法取模模板

LL (LL a, LL b, LL mod){  
    LL res = 0LL; 
    while(b) {
        if(b & 1) res =(res + a) % mod;
        a = (a + a) % mod;
        b >>= 1;
    }
    return res;
}

LL (LL a, LL b, LL mod){  ///快速乘法取模
    LL res = 0LL; 
    while(b) {
        if(b & 1) res =(res + a) % mod;
        a = (a + a) % mod; ///每次扩大2倍
        b >>= 1;
    }
    return res;
}
LL quick_mod(LL a, LL b, LL mod) { ///快速幂取模
    LL res = 1LL; ///注意初始值为1
    while(b) {
        if(b & 1) res = quick_mul(res, a, mod);
        /// res = res * a % mod;
        a = quick_mul(a, a, mod);
        ///a = a * a % mod;
        b >>= 1;
    }
    return res;
}