Question

Testing for a prime number by testing divisibility is a bit inefficient. One method to ​efficiently find prime numbers is to use what is called a “prime sieve” algorithm. Check out the following link to learn more about a famous instance of such an algorithm. ​ https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes The Sieve of Eratosthenes is a method for finding all prime numbers up to a given number. Your task​ is to write a program that defines an array of 100 boolean values. Your goal is to implement the Sieve of Eratosthenes, which will take this array of 100 values and set all the prime indices​ to ​true​ and ​false​ otherwise. For example, let ​A​ be our array. Then ​A[2]​ will be ​true​ and ​A[4]​ would be ​false, ​etc. C++

please new solution not copied thank you

Answer 1

C++ code

============================================================================================

#include<iostream>

using namespace std;

void Sieve_of_Eratosthene(bool A[],int n)
{
   int k=2;

   while(k*k<=n)
   {
   //check if number is prime
   if (A[k] == true)
   {
       for(int j=k*2;j<=n;j+=k)
       {
           A[j] = false;
       }
      
   }
   k++;
  
}

  
}

int main()
{
int n=100;
bool A[n+1];

//set bool array to true
for(int i=0;i<=n;i++)
A[i]=true;

Sieve_of_Eratosthene(A,n);

cout <<"Prime numbers using sieve of ethoresis method upto 100: "<<endl;
  
for(int i = 2; i <=n; i++)
{
if (A[i] == true)
{
cout << i << " ";
}
}

cout << endl;

return 0;
}

============================================================================================

Output