UVa-10139 Factovisors -（阶乘的整除）

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计算数 m 和数 2 ~n 的 GCD，若 GCD > 1，则 m /= GCD，若最后 m 不为 1 则表明 m 不能整除 n!，

代码：

#include<iostream>#include<string>#include<cstdio>#include<algorithm>#include<cmath>#include<iomanip>#include<queue>#include<cstring>#include<map>using namespace std;#define M 1000005typedef long long ll;int gcd(int a,int b){    return b==0?a:gcd(b,a%b);}bool isprime(int x){    double tx=sqrt(1.0*x);    int it=2;    while(it<=tx&&x%it!=0)        it++;    if(it>tx)        return true;    else        return false;}/*bool isprime(int number){    if (number == 2)        return true;    if (number % 2 == 0)        return false;    for (int c = 3; c <= ceil(sqrt(1.0*number)); c += 2)        if (number % c == 0)            return false;    return true;}*/int main(){    int n,m;    while(scanf("%d%d",&n,&m)!=EOF)    {        if(m==0)        {            printf("%d does not divide %d!\n",m,n);            continue;        }        if(m==1)        {            printf("%d divides %d!\n",m,n);            continue;        }        if(isprime(m)&&m>n)        {            printf("%d does not divide %d!\n",m,n);            continue;        }        if(m<=n)        {            printf("%d divides %d!\n",m,n);            continue;        }        bool flag=false;        int tm=m;        int gc;        for(int i=n;i>=2;i--)        {            gc=gcd(tm,i);            if(gc>1)            {                tm=tm/gc;                if(tm<i)                {                    flag=true;                    break;                }                if(isprime(tm))                {                    break;                }            }        }        if(flag)            printf("%d divides %d!\n",m,n);        else            printf("%d does not divide %d!\n",m,n);    }    return 0;}

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