ACdream 1007 a + b (数学+快速幂)

题目链接：
ACdream 1007

题目：

题解：这个快速幂的相乘会爆long long，用快速乘就可以了。
不说了….看代码吧…

AC代码：

/** this code is made by LzyRapx* Problem: 1007* Verdict: Accepted* Submission Date: 2017-06-22 17:43:18* Time: 176MS* Memory: 1664KB*/#include <bits/stdc++.h>using namespace std;typedef long long ll;const ll mod = 10000000007LL;ll Multi(ll a, ll b)//a*b{    ll ans = 0;    while(b)    {        if(b&1){            ans = (ans + a) % mod ;        }        a = (a<<1) % mod;        b>>=1;        }    return ans%mod ;}ll BigMulti(ll ans , ll K){    if(ans == 0 && K ==0)return 1;    if(ans == 0)return 0;    ll res = 1;    while(K)    {        if(K&1){            res = Multi(ans,res);        }        ans = Multi(ans , ans);        K >>= 1;     }    return res%mod ;}ll N,K;int main(){    int t ;    scanf("%d",&t);    while(t--)    {        scanf("%lld%lld",&N,&K);        ll res = 0, ans;        for(int i=1;i<=N;i++)        {            scanf("%lld",&ans);            ans %= mod;            ans = (ans + mod ) % mod;            res = (res + BigMulti(ans,K)%mod + mod) % mod;         }        printf("%lld\n",res);     }    return 0; }