Cycle-04. Verifying "Goldbach conjecture" (20)

Source of the topic:
Cycle-04. Verify "Goldbach conjecture" (20) time limit of MS
Memory Limit 65536 KB
Code length limit 8000 B
Procedures for the award of questions StandardAuthor Xu Jianchun (Zhejiang University)

The famous "Goldbach conjecture" in the field of mathematics roughly means that any even number greater than 2 is always represented as the sum of two primes. For example: 24=5+19, where 5 and 19 are prime numbers. The task of this experiment is to design a program to verify that the even number within 2 billion can be decomposed into a sum of two primes.

Input format:

The input gives an even n in the range of (2, 2 000 000 000] in a row.

Output format:

In a row, according to the format "n = p + q" The prime number of the output n is decomposed, where P <= Q are prime. And because such decomposition is not unique (for example, 24 can also be decomposed into 7+17), it is necessary to output all the solutions of the P smallest solution.

Input Sample:

24

Sample output:

24 = 5 + 19

Code:

Import Java.io.ioexception;import java.text.decimalformat;import Java.text.parseexception;import Java.util.Scanner  ;p Ublic class Main {public  static void Main (string[] args) throws ParseException, IOException {          Scanner Scanner = New Scanner (system.in);    Long N;    a A, a, two primes long A, b;    Enter a word number    n = Scanner.nextlong ();    Starting from (2,n] The loop to find the prime number for    (long i=2; i<n; i++)    {    //Determine if it is a prime    if (Isprimenumber (i))    {    a=i;    B=n-i;        if (Isprimenumber (b))    {    //Let large numbers row in front of    if (a>b)        {        long temp;        Temp =a;        A=  B;        b= temp;        }    System.out.println (n+ "=" +a+ "+" +b);    Break      ;    }}}} public static Boolean Isprimenumber (long N)  {    //1 is not a prime  if (n ==1) return false;  To determine if I is a prime number, simply remove each integer between 2~ radical I for  (Long i = 2;I<=MATH.SQRT (n); i++)  {  if (n%i==0) return false;  }  return true;  }}              

Reference:

http://blog.csdn.net/summercpp/article/details/38326679

Http://zuoye.baidu.com/question/dc086c6a0655d55493b45d27b4272b4c.html

Cycle-04. Verifying "Goldbach conjecture" (20)