hdu 2204 Eddy's爱好（容斥原理）

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弱的第一发容斥...光看别人题解理解别人思路花了四十分钟- -果然组合数学这块还是太弱了- -

参考了cxlove大神的博客。附上链接：点击打开链接

#include<cstring>#include<cstdio>#include<cstdlib>#include<cmath>#include<algorithm>#include<iostream>using namespace std;#define ll long longint ss[30]={2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59};ll n,i,ans;void dfs(int pos,int num,int k){    if(k==0)    {        ll tmp=pow(n,1.0/num);        if(pow(tmp,0.0+num)>n) tmp--;//判断越界        tmp--;        if(tmp>0)            ans=ans+((i&1)?1:-1)*tmp;        return ;    }    if(pos>=17) return ;    if(num*ss[pos]<=60)        dfs(pos+1,num*ss[pos],k-1);    dfs(pos+1,num,k);}int main(){    while(scanf("%I64d",&n)!=EOF)    {        ans=0;        for(i=1;i<=3;i++)            dfs(0,1,i);        cout<<ans+1<<endl;    }    return 0;}

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