Sumdiv
Time Limit: 1000MS Memory Limit: 30000K
Total Submissions: 24296 Accepted: 6022
Description
Consider two natural numbers A and B. Let S be the sum of all natural divisors of A^B. Determine S modulo 9901 (the rest of the division of S by 9901).
Input
The only line contains the two natural numbers A and B, (0 <= A,B <= 50000000)separated by blanks.
Output
The only line of the output will contain S modulo 9901.
Sample Input
2 3
Sample Output
15
Hint
2^3 = 8.
The natural divisors of 8 are: 1,2,4,8. Their sum is 15.
15 modulo 9901 is 15 (that should be output).
Source
Romania OI 2002
题意:求
题意很简单。思路:
1)整数唯一分解定理
2)约数求和
3)快速幂
#include<algorithm>
#include<stdio.h>
#include<iostream>
#include<string>
#include<string.h>
using namespace std;
typedef long long int ll;
const int MOD=9901;
const int N=10000+10;
int p[N],n[N];
ll power(ll p,ll n)
{
ll sq=1;
while(n)
{
if(n&1)
sq=(sq*p)%MOD;
n>>=1;
p=(p*p)%MOD;
}
return sq;
}
ll sum(ll p,ll n)
{
if(n==0)
return 1;
if(n%2==0)
return (sum(p,n/2-1)*(1+power(p,n/2+1))+power(p,n/2))%MOD;
else
return (sum(p,n/2)*(1+power(p,n/2+1)))%MOD;
}
int main()
{
int a,b;
while(~scanf("%d%d",&a,&b))
{
int k=0;
for(int i=2;i*i<=a;)
{
if(a%i==0)
{
p[++k]=i;
n[k]=0;
while(!(a%i))
{
n[k]++;
a/=i;
}
}
if(i==2)
i++;
else
i+=2;
}
if(a!=1)
{
p[++k]=a;
n[k]=1;
}
int ans=1;
for(int i=1;i<=k;i++)
{
ans=(ans*sum(p[i],n[i]*b)%MOD)%MOD;
}
printf("%d\n",ans);
}
return 0;
}