学步园

以下代码用于验证 大于 4 小于 500的一个偶数可以拆分成两个素数之和。

#pragma once
class CJudegeprime
{
public:
	CJudegeprime(void);
	~CJudegeprime(void);
private:
	bool isprime(int m);
	int  getallprime100(int container[]);	
	bool judgeisinarray(int number, int container[], int count, int start);
	bool decompose(int even);
public:
	void makelist();
	void display();

};


#include "StdAfx.h"
#include "Judegeprime.h"
#include "math.h"


CJudegeprime::CJudegeprime(void)
{
}


CJudegeprime::~CJudegeprime(void)
{
}

bool CJudegeprime::isprime(int m)
{
	int loopcount = (int)sqrt(long double(m));
	for(int i=2; i<=loopcount; i++)
	{
		if (m % i == 0)
		{
			return false;
		}
	}
	return true;
}

int CJudegeprime::getallprime100(int container[])
{
	int outcome = 0;
	for(int i=2; i<500; i++)
	{
		if (isprime(i))
		{
			container[outcome] = i;
			outcome++;
		}
	}
	return outcome;
}

void CJudegeprime::display()
{
	int container[500];
	int count = getallprime100(container);
	for(int i = 0; i<count; i++)
	{
		printf("index=%d prime=%d\n", i, container[i]);
	}
}

bool CJudegeprime::decompose(int even)
{
	int container[500];
	int count = getallprime100(container);
	for(int i=0; i<count; i++)
	{
		if (container[i] < even)
		{
			int temp = even - container[i];
			if (judgeisinarray(temp, container, count, i))
			{
				printf("%d = %d + %d\n", even, container[i] , temp);
				return true;
			}
		}
		else
		{
			break;
		}
	}
	return false;
}

bool CJudegeprime::judgeisinarray(int number, int container[], int count, int start)
{
	for(int i=start; i<count; i++)
	{
		if (number == container[i]) return true;
	}
	return false;
}

void CJudegeprime::makelist()
{
	for(int i=4; i<500; i+=2)
	{
		decompose(i);
	}
}

主函数验证：

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

#include "stdafx.h"
#include "Judegeprime.h"


int _tmain(int argc, _TCHAR* argv[])
{
	CJudegeprime jp;
	//jp.display();
	printf("*********************\n");
	jp.makelist();

	getchar();
	return 0;
}