RXD and math
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 524288/524288 K (Java/Others)
Total Submission(s): 310 Accepted Submission(s): 160
Problem Description
RXD is a good mathematician.
One day he wants to calculate:
output the answer module .
are different prime numbers
Input
There are several test cases, please keep reading until EOF.
There are exact 10000 cases.
For each test case, there are 2 numbers .
Output
For each test case, output "Case #x: y", which means the test case number and the answer.
Sample Input
10 10
Sample Output
Case #1: 999999937
Source
2017 Multi-University Training Contest - Team 3
首先看出来u()函数是莫比乌斯函数
然后手动打表找出来的规律,发现结果为n的k次方
利用快速幂直接求就可以了
#include<cstdio>
#include<iostream>
using namespace std;
const long long int mod=1e9+7;
long long int fast_pow_mod(long long int a,long long int b)
{
long long int res=1;
while(b)
{
if(b&1) res=res*a%mod;
a=((a%mod)*(a%mod))%mod;
b>>=1;
}
return res;
}
int main()
{
long long int n,k;
long long int cas=1;
while(scanf("%lld%lld",&n,&k)!=EOF)
{
long long int w;
w=fast_pow_mod(n,k);
printf("Case #%lld: %lld\n",cas++,w%mod);
}
return 0;
}
不是数学方面的,直接从网上捞了个快速幂模板发现wa了一次,后来自己写了一遍,发现是爆long long 了,过程中也要mod