快速幂 --- CSU 1556: Jerry's trouble

 Jerry's trouble

Problem's Link:   http://acm.csu.edu.cn/OnlineJudge/problem.php?id=1556

---

 

Mean: 

略。

analyse:

水题，直接快速幂。

Time complexity: O(n)

 

Source code: 

 

//  Memory   Time 

//  1347K     0MS 

//   by : crazyacking 

//   2015-03-29-19.18 

#include<map> 

#include<queue> 

#include<stack> 

#include<cmath> 

#include<cstdio> 

#include<vector> 

#include<string> 

#include<cstdlib> 

#include<cstring> 

#include<climits> 

#include<iostream> 

#include<algorithm> 

#define MAXN 1000010 

#define LL long long 

using namespace std; 

const LL MOD=1e9+7; 

  

LL quick_pow(LL a,LL b,LL m) 

{ 

        LL ans=1; 

        while(b) 

        { 

                if(b&1) 

                { 

                        ans*=a; 

                        ans%=m; 

                } 

                a*=a; 

                a%=m; 

                b/=2; 

        } 

        return ans%m; 

} 

  

int main() 

{ 

        ios_base::sync_with_stdio(false); 

        cin.tie(0); 

//      freopen("C:\\Users\\Devin\\Desktop\\cin.cpp","r",stdin); 

//      freopen("C:\\Users\\Devin\\Desktop\\cout.cpp","w",stdout); 

        LL n,m; 

        while(cin>>n>>m) 

        { 

                LL sum=0; 

                for(int i=1;i<=n;++i) 

                { 

                        sum+=quick_pow(i,m,MOD); 

                        sum%=MOD; 

                } 

                cout<<sum%MOD<<endl; 

        } 

        return 0; 

} 

/* 

  

*/

  

/************************************************************** 

    Problem: 1556 

    User: crazyacking 

    Language: C++ 

    Result: Accepted 

    Time:2704 ms 

    Memory:1476 kb 

****************************************************************/

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