n个数中求指定的位数的最大最小公倍数

#include <stdio.h>

#define MAX 1000001



int prime[MAX];

__int64 lcm = 0;



void PrimeNum()

{

	int i, j;

	for(i = 0; i < MAX; i++)

		prime[i] = 1;

	for(i = 2; i*i < MAX; i++)

	{

		if(prime[i]==1)

		{

			for(j=2*i; j<MAX; j+=i)

				prime[j] = 0;	

		}					

	}	

}



__int64 Gcd(__int64 m, __int64 n)

{

	__int64 r;

	if(m < n)

		{

			r = m;

			m = n;

			n = r;	

		}	

	

	while(n != 0)

	{

		r = m%n;

		m = n;

		n = r;	

	}

	return m;

}



void Feasible(__int64 result[])

{

	__int64 gcd, temp;

	gcd = Gcd(Gcd(result[0], result[1]), result[2]);

	temp = result[0]*result[1]*result[2] / gcd;

	if(temp > lcm) lcm = temp;

}



void Greedy(__int64 n)

{

	__int64 result[3]={n,n-1,n-2};

	__int64 i, m, k=n, temp;

	Feasible(result);

	for(m = 2; m>=0; m--)

	{

		for(i = n-3; prime[i]==0; i--)

		{

			result[m] = i;

			Feasible(result);	

		}

		result[0] = n;

		result[1] = n-1;

		result[2] = n-2;

	}

	while(prime[k]==0) k--;

	temp = n*(n-1)*k;

	if(temp > lcm) lcm = temp;	

	printf("%I64d", lcm);	

}



int main()

{

	__int64 n;

	scanf("%I64d", &n);

	PrimeNum();

	Greedy(n-1);

	system("pause");

	return 0;	

}