Prime k-tuple UVA - 1404

 

    一个步骤：  在[ a, b] 中标记 S 的倍数

 

#include<iostream>
#include<cstring>
#include<algorithm>
#include<vector>
using namespace std;
const int N=1e5+20;
const int Q=2e9+2;
#define int long long
 bool vis[Q]; 
 int b[N], pm[N],tot=0;
 
 void init(int top){
    b[1]=1;
    for(int i=2;i<=top;i++){
        if(b[i]) continue;
        pm[++tot]= i;
        for(int j=2;j*i<=top;j++) b[j*i]=1;
    }
 }
 void sov () {
 	vector<int> vec;
    int ret = 0;
    int a, b, s, k;
    memset(vis, 0, sizeof(vis));
 
    cin>>a>>b>>k>>s;
 // 对于质数I， 筛出[a,b] 之间I 的倍数
    for (int i =1; i <=tot && pm[i] * pm[i] <= b; i++) {
        int u = pm[i];int d = (u - a % u) % u;
        if (u == a + d) d += u;
 
        while (d <= b - a) {
            vis[d] = 1;
            d += u;
        }
    }
 
    for (int i = 0; i <= b-a; i++) {
        if (vis[i] == 0 && a + i > 1)
            vec.push_back(a+i);
    }
 
 
    for (int i = 0; i + k - 1 < vec.size(); i++) {
        if (vec[i+k-1] - vec[i] == s)
            ret++;
    }
 
    cout<<ret<<endl;
}
 signed main () {
    init(1e5);
 
    int cas; cin>>cas;
    while (cas--) 
        sov();
}