题目:
Easy Summation
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)Total Submission(s): 969 Accepted Submission(s): 391
Problem Description
You are encountered with a traditional problem concerning the sums of powers.
Given two integers n and k. Let f(i)=ik, please evaluate the sum f(1)+f(2)+...+f(n). The problem is simple as it looks, apart from the value of n in this question is quite large.
Can you figure the answer out? Since the answer may be too large, please output the answer modulo 109+7.
Given two integers n and k. Let f(i)=ik, please evaluate the sum f(1)+f(2)+...+f(n). The problem is simple as it looks, apart from the value of n in this question is quite large.
Can you figure the answer out? Since the answer may be too large, please output the answer modulo 109+7.
Input
The first line of the input contains an integer T(1≤T≤20),
denoting the number of test cases.
Each of the following T lines contains two integers n(1≤n≤10000) and k(0≤k≤5).
Each of the following T lines contains two integers n(1≤n≤10000) and k(0≤k≤5).
Output
For each test case, print a single line containing an integer modulo 109+7.
Sample Input
3 2 5 4 2 4 1
Sample Output
33 30 10
代码:
#include<stdio.h>
#include<iostream>
using namespace std;
const int maxn=1e4+10;
const int mod=1e9+7;
int main(){
long long t,n,k;
scanf("%lld",&t);
long long ans;
while(t--){
scanf("%lld%lld",&n,&k);
ans=0;
for(long long i=1;i<=n;++i){
long long tmp=1;
for(long long j=1;j<=k;++j) tmp=tmp*i%mod;//这里没注意到取模 WA了两发
ans+=tmp;
ans%=mod;
}
printf("%lld\n",ans);
}
return 0;
}