OJ Board

Code: Select all

#include<stdio.h>
#include<math.h>

long long a[100000],c,flag[1000000],b[10000][10000];

void seive(long long n)
{
	long long k,i,j,r;
	k=sqrt(n);
	for(i=1;i<=n;i++)
		flag[i]=0;
	flag[1]=1;
	a[0]=2;
	c=1;
	for(i=4;i<=n;i+=2)
		flag[i]=1;
	for(i=3;i<=n;i+=2)
	{
		if(flag[i]==0)
		{
			a[c++]=i;
			if(k>=i)
			{
				r=i+i;
				for(j=i*i;j<=n;j+=r)
					flag[j]=1;
			}
		}
	}
	a[c]=0;
}

int main()
{ 
	long long n,f,i,p,j;
	seive(200000);
	while(scanf("%lld",&n)==1&&n>0)
	{
		if(n==1)
		{
			printf("(3, 5)\n");
			continue;
		}
		j=1;
		for(i=6;;i+=6)
		{
			if(flag[i-1]==0&&flag[i+1]==0)
			{
				j++;
				if(j==n)
				{
					printf("(%lld, %lld)\n",i-1,i+1);
					break;
				}
			}
		}
	}
	return 0;
}

Code: Select all

#include<stdio.h>
bool sieve[20000001];
long int primes[100001];
int main()
{
    long int i,j,k,n,c;
    sieve[0]=sieve[1]=0;
    for(i=2; i<20000001; i++)  sieve[i]=1;
    for(i=0; i<4473; i++)
    {
             if(sieve[i]!=0)
             {
                            for(j=i+1; j<20000001; j++)
                            {
                                       if(sieve[j]!=0)
                                       {
                                                      if((j%i)==0)  sieve[j]=0;
                                                      }
                                       }
                            }
             }
    j=2;
    i=7;
    primes[1]=3;
    while(i<20000001)
    {
             if(sieve[i-1]==1 && sieve[i+1]==1)
             {
                            primes[j]=i-1;
                            j++;
                            i+=6;
                            }
             else i+=2;
             }
    
    while(scanf("%ld",&n)==1)
    {
           
           printf("(%ld, %ld)\n",primes[n],primes[n]+2);
           }
    return 0;
}

Code: Select all

for(j = i+1; (!prime_number[j]);j++) ;

Code: Select all

for(j = i+1; (!prime_number[j]) && j<n;j++) ;

Code: Select all

import java.util.*;
import java.math.*;
import java.text.*;
import java.lang.*;

class Main
{
	public static void main(String abyss[])throws Exception
	{
		Scanner sc = new Scanner(System.in);
	
		ArrayList<Integer> al = new ArrayList<Integer>();
		ArrayList<Integer> prime = new ArrayList<Integer>();
		boolean primeCase[] = new boolean[20000001];
		Arrays.fill(primeCase, true);
		primeCase[0]=primeCase[1]=false;
		
		for(int a=2; a<primeCase.length; a++)
		{
			if(primeCase[a])
			{
				for(int b=2; b*a<primeCase.length; b++)
				{
					primeCase[b*a] = false;
				}
			}
		}
		al.add(0,2);
		for(int a=3; a<20000001; a++) // checking if prime number and assigning value in arraylist
		{
			if(primeCase[a]==true)
			{
				al.add(al.size(),a);
			}
		}
		prime.add(0,2);
		for(int a=1; a<al.size()-1; a++)
		{
			if(al.get(a+1)-al.get(a)==2)
			{
				prime.add(prime.size(), al.get(a));
			}
		}
		while(sc.hasNextLine())
		{
			String input = sc.nextLine();
			if(input.length()==0)
				break;
					
			int num = Integer.parseInt(input);
			int sum = prime.get(num)+(2);
			System.out.println("("+prime.get(num)+", "+sum+")");
		}
		
		prime.clear();
		al.clear();
	}

}