[笔记] 快速乘

[笔记] 快速乘

快速幂中都换成加号,初始化是(0).

ll q_times(ll a, ll b){
    ll w = 0;
    while(b){
        if(b & 1)
            w = (w + a) % Mod;
       	b >>= 1;
        a = (a + a) % Mod;
    }
    return w;
}