Friday, 29 July 2016
Problem : Consecutive Prime Sum Some prime numbers can be expressed as Sum of other consecutive prime numbers. For example 5 = 2 + 3 17 = 2 + 3 + 5 + 7 41 = 2 + 3 + 5 + 7 + 11 + 13 Your task is to find out how many prime numbers which satisfy this property are present in the range 3 to N subject to a constraint that summation should always start with number 2. Write code to find out number of prime numbers that satisfy the above mentioned property in a given range.
import java.util.*;
class Prime{
public static void main(String []args)
{
int count=0,p=2,i;
Scanner sc=new Scanner(System.in);
int n=sc.nextInt();
int a[]=new int[n+1];
for(i=0;i<=n;i++)
{
a[i]=i;
}
for(p=2;p*p<=n;p++)
{
if(a[p]!=0)
{
for(i=p*2;i<=n;i+=p)
{ a[i]=0;
}
int sum=5;
for(i=5;i<=n+2;i=i+2){
if((a[i]!=0 && a[i]==sum)||a[i]==-1)
count=count+1;
if (a[i] != 0 || a[i] == -1)
sum=sum+i;
if(a[sum]!=0)
a[sum]=-1;
}
}
}
System.out.print(count);
}
}
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