【Violet 5】【BZOJ2721】樱花

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Description
这里写图片描述
Input

Output

Sample Input
3
Sample Output
9
HINT

Source

interviewstreet–EQUATIONS

我良心的在这里给泥萌加上了样例>_<
SD2015省队集训Week1的测试题

首先显然x>n!,y>n!,那么我们选择令y=n!+z
则显然有x=n!2z+n!
求出n!2的约数个数就行了
答案记得开longlong,中间过程会炸

#include<iostream>#include<cstdio>#include<cstring>#include<cmath>#include<algorithm>#define MAXN 1000010#define P 1000000007using namespace std;int n;long long ans=1;int prime[MAXN],top,fac[MAXN];bool not_prime[MAXN];int cnt[MAXN];void check_prime(){    for (int i=2;i<=n;i++)    {        if (!not_prime[i])  prime[++top]=i,fac[i]=top;        for (int j=1;j<=top&&i*prime[j]<=n;j++)        {            not_prime[i*prime[j]]=1;fac[i*prime[j]]=j;            if (i%prime[j]==0)  break;        }    }}void calc(int x){    while (x!=1)    cnt[fac[x]]++,x/=prime[fac[x]];}int main(){    scanf("%d",&n);    check_prime();    for (int i=1;i<=n;i++)  calc(i);    for (int i=1;i<=top;i++)    ans=ans*((2*cnt[i]+1)%P)%P;    cout<<ans<<endl;}

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