Erato Sieve Method (Sieve of Eratosthenes) to calculate the prime number.

The Erato method (Sieve of Eratosthenes) is a method for finding all primes less than n.
Start by creating an integer 2~n table, looking for I? Integer, which is programmed to implement this algorithm, and discusses the computational time.

Since they are implemented by deletion, and 1 and 0 are not prime numbers, they are removed from 2,3,5 and their multiples.

Use data[] to store all the numbers, replacing the good number in the presence of data[]

Instead, just make the 2,3,5 and the number that divides the numbers to zero: if (data[j]% i = = 0) data[j]==0;

The code snippet implemented is:

for (i = 2; i < n; i++) for (j = i + 1; j < N; j + +) if (data[j]! = 0 && data[j]% i = = 0) Data[j] = 0;

So the final complete implementation process is:

#include <iostream> #include <math.h>using namespace std; #define MAX 50000int n;int data[max];class rox{ Public:void Show (), void creat (), void Run ();p rivate:int I, J;}; void Rox::creat () {for (i = 0; I <= N; i++) data[i] = i;} void Rox::run () {for (i = 2, i < n; i++) {for (j = i + 1; j < N; j + +) {if (data[j]! = 0 && data[j]% i = = 0) Dat A[J] = 0;}}} void  Rox::show () {for (i = 0; I <=n; i++) {if (Data[i]! = 0&&data[i]!=1) cout << "" <<data[i];}} void Main () {Rox t;cout << "Please enter the maximum value tested N:"; cin >> N; T.creat (); cout << "The table created is" << Endl; T.show (); T.run (); cout<<endl;cout << "Deleted tables are:" << Endl; T.show (); cout << Endl;}

　　

Erato Sieve Method (Sieve of Eratosthenes) to calculate the prime number.