Foreword
Erichsen sieve is a method of 2-n prime sieve, but the time complexity is not strong Euler screen, only O (n-* log log) but also a better understanding of the sieve
text
One, the prime basis Definitions
It refers to the prime natural numbers greater than 1, in addition to 1 and itself no other factors natural number. (Excerpt from Baidu Encyclopedia)
Second, the algorithm Detailed
All the 2-n number is marked as true, and then again scan cycle, respectively, each of the multiple number of marks to false (off screen), and so on.
Third, code implementation
1 #include<bits/stdc++.h>
2 using namespace std;
3 const int maxn=1e6;
4 long long cc[maxn];
5 bool vis[maxn];
6 long long sum;
7 / * start screen prime function * /
8 void prime(int n)
9 {
// sum statistics for the number of prime numbers; 10 sum = 0
11 memset (vis, true, sizeof vis); // array vis all the flag is true
12 for(int i=2;i<=n;++i)
13 {
14 if(vis[i])
15 {
16 sum ++; // sum increases with the number of prime numbers increase
17 cc [sum] = i; // the prime number stored in the array cc
18 for(int j=2*i;j<=n;j+=i)
19 {
20 vis [j] = false; // the number is not a prime number flag to false
21 }
22 }
23 }
24 }
25 / * end function * /
26 int main ()
27 {
28 int n;
29 cin>>n;
30 / * for n = 1 is judged Laid * /
31 if(n==1)
32 {
33 cout<<"Possible"<<endl;
34 }
35 / * end * special judge /
36 prime (n);
37 for(int i=1;i<=sum;++i)
38 {
39 cout << cc [i] << ""; // output to
40 }
41 return 0;
42 }
43