Page 603 - Computer science 868 Class 12
P. 603

Program 15    A Goldbach number is a positive even integer that can be expressed as the sum of two odd
                                 primes.
                                 Note: All even integer numbers greater than 4 are Goldbach numbers.
                                 Example:
                                 6 = 3 + 3
                                 10 = 3 + 7
                                 10 = 5 + 5

                                 Hence, 6 has one odd prime pair 3 and 3. Similarly, 10 has two odd prime pairs, i.e., 3 and 7,
                                 5 and 5.
                                 Write a program to accept an even integer 'N' where N > 9 and N < 50. Find all the odd prime
                                 pairs whose sum is equal to the number 'N'.

                   1       import java.util.*;
                   2       class GoldBatch

                   3       { int n;
                   4         GoldBatch(int nn)

                   5         { n=nn;}
                   6         int isPrime(int a)

                   7         { int c=0;
                   8           for(int i=1;i<=a;i++)

                   9           { if(a%i==0)
                   10              c++;

                   11          }
                   12          return c;

                   13        }
                   14        void check()

                   15        {   int r1,r2,i,j;
                   16            if(n<=9 || n>=50 )

                   17              System.out.println("INVALID INPUT NUMBER OUT OF RANGE");
                   18            else if(n%2!=0)
                   19              System.out.println("INVALID INPUT NUMBER IS ODD ");

                   20            else

                   21            {  System.out.println("Sum of prime numbers are");
                   22                for(i=3;i<=n;i=i+2)
                   23               { r1=isPrime(i);

                   24                 for(j=i;j<=n;j=j+2)






                                                                                                                       601
                                                                                                   Internal Assessment  601
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