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'.
Answers
Answer:
Explanation: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. Hence, 6 has one odd prime pair 3 and 3. Similarly, 10 has two odd prime pairs, i.e. 3, 7 and 5, 5.
Answer:
import java.util.Scanner;
public class GoldbachNumber
{
public static boolean isPrime(int num) {
int c = 0;
for (int i = 1; i <= num; i++) {
if (num % i == 0) {
c++;
}
}
return c == 2;
}
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("ENTER THE VALUE OF N: ");
int n = in.nextInt();
if (n <= 9 || n >= 50) {
System.out.println("INVALID INPUT. NUMBER OUT OF RANGE.");
return;
}
if (n % 2 != 0) {
System.out.println("INVALID INPUT. NUMBER IS ODD.");
return;
}
System.out.println("PRIME PAIRS ARE:");
int a = 3;
int b = 0;
while (a <= n / 2) {
b = n - a;
if (isPrime(a) && isPrime(b)) {
System.out.println(a + ", " + b);
}
a += 2;
}
}
}