hdu 6134 Battlestation Operational 莫比乌斯反演

题目链接点这里

#include<bits/stdc++.h>using namespace std;#define INF 0x3f3f3f3f#define INFLL 0x3f3f3f3f3f3f3f3f#define FIN freopen("in.txt","r",stdin);#define mem(x,y) memset(x,y,sizeof(x));typedef unsigned long long ULL;typedef long long LL;#define fuck(x) cout<<x<<endl;#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1typedef pair<pair<int, int>, int> PIII;typedef pair<int, int> PII;const double eps = 1e-8;const double PI = acos(-1);const int P = 1e9 + 7;const int MX = 2e6 + 5;int n, L;bool isprime[MX];int prime[MX], mu[MX] = {0, 1};LL pre[MX];LL preu[MX];void mubi(){    memset(isprime, true, sizeof(isprime));    int primecount = 0;    for (int i = 2; i < MX; ++i)    {        if (isprime[i])        {            prime[++primecount] = i;            mu[i] = -1;        }        for (int j = 1; j <= primecount && i * prime[j] < MX;  ++j)        {            isprime[i * prime[j]] = false;            if (i % prime[j] == 0)            {                mu[i * prime[j]] = 0;                break;            }            else mu[i * prime[j]] = -mu[i];        }    }    memset(pre, 0, sizeof(pre));    for (int i = 1; i < MX; i++)    {        pre[i]++;        pre[i + 1]--;        for (int j = 2; j * i <MX; j++)        {            pre[j * i + 1] = (pre[j * i + 1] - j + P) % P;            pre[j * i - i + 1] = (pre[j * i - i + 1] + j) % P;        }    }    for (int i = 1; i < MX; i++)pre[i] = (pre[i] + pre[i - 1] + P) % P;    for (int i = 1; i < MX; i++)pre[i] = (pre[i] + pre[i - 1] + P) % P;    preu[0] = 0;    for (int i = 1; i < MX; i++)preu[i] = (preu[i - 1] + mu[i] + P) % P;}int main(){    mubi();    FIN;    while (cin >> n)    {        LL ans = 0;        int t = (int)sqrt(n);        for (int i = 1; i <= min(t, n); i++)        {            ans = (ans + mu[i] * pre[n / i]) % P;        }        t = n / t;        for (int i = t - 1; i >= 1; i--)        {            int r = n / i;            int l = n / (i + 1);            LL sum = (P + preu[r] - preu[l]) % P;            ans = (ans + sum * pre[i]) % P;        }        printf("%lld\n", ans);    }    return 0;}