Acdream a + b

http://acdream.info/problem?pid=1007

两个 long long 相乘会超long long

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <algorithm>

 4 #define ll long long

 5 #define maxn 10000

 6 #define mod 10000000007

 7 using namespace std;

 8 

 9 ll a[maxn];

10 ll n,k,t;

11 ll fMul(ll a, ll b) {

12     ll t = 0, y = a;

13     while(b) {

14         if(b & 1) t = (t + y) % mod;

15         y = (y + y) % mod;

16         b >>= 1;

17     }

18     return t;

19 }

20 

21 ll modExp(ll a, ll b) {

22     ll t = 1, y = a;

23     while(b) {

24         if(b & 1) t = (fMul(t, y)) % mod;

25         y = (fMul(y, y)) % mod;

26         b >>= 1;

27     }

28     return t;

29 }

30 

31 int main()

32 {

33       scanf("%lld",&t);

34       while(t--)

35       {

36           scanf("%lld%lld",&n,&k);

37           ll sum=0;

38           for(int i=0; i<n; i++)

39           {

40               scanf("%lld",&a[i]);

41           }

42           for(int i=0; i<n; i++)

43           {

44               a[i]=((a[i]%mod)+mod)%mod;

45               ll c=modExp(a[i],k);

46               sum=(sum+c)%mod;

47           }

48           printf("%lld\n",sum);

49       }

50       return 0;

51 }

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