lightoj1197区间素数筛

模板题，不过好像有点问题，当a==1的时候，答案把一也算进去了，要减去

#include<map>

#include<set>

#include<cmath>

#include<queue>

#include<stack>

#include<vector>

#include<cstdio>

#include<cassert>

#include<iomanip>

#include<cstdlib>

#include<cstring>

#include<iostream>

#include<algorithm>

#define pi acos(-1.0)

#define ll long long

#define mod 1000000007

#define ls l,m,rt<<1

#define rs m+1,r,rt<<1|1

#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;

const double g=10.0,eps=1e-;

const int N=+,maxn=+,inf=0x3f3f3f;

bool prime[N],primesmall[N];

ll seg_prime(ll a,ll b)

{

    memset(prime,,sizeof prime);

    for(ll i=;i*i<b;i++)primesmall[i]=;

    for(ll i=;i<=b-a;i++)prime[i]=;

    for(ll i=;i*i<b;i++)

    {

        if(primesmall[i])

        {

            for(ll j=*i;j*j<b;j+=i)primesmall[j]=;

            for(ll j=max((ll),(a+i-)/i)*i;j<=b;j+=i)prime[j-a]=;

        }

    }

    ll ans=;

    for(ll i=;i<=b-a;i++)

        if(prime[i])

           ans++;

    return ans;

}

int main()

{

    ios::sync_with_stdio(false);

    cin.tie();

    ll t,cnt=;

    cin>>t;

    while(t--){

        ll a,b;

        cin>>a>>b;

        if(a==)cout<<"Case "<<++cnt<<": "<<seg_prime(a,b)-<<endl;

        else cout<<"Case "<<++cnt<<": "<<seg_prime(a,b)<<endl;

    }

    return ;

}

/*********************

9

2 36

3 73

3 11

1 1

1 2

2147383647 2147483647

23990500 24000500

24000501 24100501

23999500 24010501

*********************/