BZOJ2440: [中山市选2011]完全平方数 容斥原理_莫比乌斯函数

emmm.......

数学题都不友好QAQ......

Code:

#include <cstdio>
#include <algorithm>
#include <cmath>
#include <cstring>
#define setIO(s) freopen(s".in","r",stdin)
#define maxn 50080
const long long inf = 1844387848;
#define ll long long
using namespace std;
int mu[maxn],vis[maxn],prime[maxn],tot;
int main(){
    //setIO("input");
    mu[1]=1;
    for(int i=2;i<maxn;++i) {
        if(!vis[i]) prime[++tot]=i,mu[i]=-1;
            for(int j=1;j<=tot&&(ll)prime[j]*i < (ll) maxn; ++j) {
                vis[prime[j]*i] = 1;
                if(i % prime[j]==0) { mu[prime[j]*i] = 0; break;  }
                mu[prime[j]*i] = -mu[i];
            }
    }
    int T;
    long long k;
    long long l,r,ans;
    scanf("%d",&T);
    while(T--){
        scanf("%lld",&k);
        l=1,r=inf,ans=0;
        while(l <= r) {
            long long mid=(l+r)>>1;
            long long tmp=0;
            for(ll i=1;i*i<=mid;++i)
                tmp+=mu[i]*(mid/(i*i)) ;
            if(tmp>=k) r = mid-1,ans=mid;
            else l = mid + 1;
        }
        printf("%lld\n",ans);
    }
    return 0;
}