c05.cpp

《C++程序设计习题及解答》配套代码VC版

// c05.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#include <iostream.h>
#include <math.h>

int isprime( long n );

int main(int argc, char* argv[])
{
	long num;
	cout << "请输入一个偶数(>=6):\n";
	cin >> num;

	for ( long n = 6; n <= num; n += 2 )
		for ( long i = 3; i <= n/2; i += 2 )
			if ( isprime( i ) && isprime( n-i ) )
			{
				cout << n << " = " << i << " + " << (n-i) << endl;
				break;
			}

	return 0;
}

int isprime( long n )
{
	long q = (long)sqrt( n );
	for ( long i = 2; i <= q; ++i )
		if ( n % i == 0 )
			return 0;

	return 1;
}