HDU 5104 Primes Problem

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5104

题面：

Primes Problem

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1776    Accepted Submission(s): 813

Problem Description

Given a number n, please count how many tuple(p1, p2, p3) satisfied that p1<=p2<=p3, p1,p2,p3 are primes and p1 + p2 + p3 = n.

 

Input

Multiple test cases(less than 100), for each test case, the only line indicates the positive integer  n(n≤10000) .

 

Output

For each test case, print the number of ways.

 

Sample Input

   
   
   
   

    
    
    
    3
9
   
   
   
   

 

Sample Output

   
   
   
   

    
    
    
    0
2
   
   
   
   

 

Source

BestCoder Round #18

 

解题：

唉，说好不刷水题的了，又刷，真是不好...

代码：

#include <iostream>
#include <cmath>
using namespace std;
int store_prime[10000],cnt=0;
bool is_prime(int x)
{
	if(x==2)return true;
	int up_limit=sqrt(1.0*x);
	for(int i=2;i<=up_limit;i++)
	{
		if(x%i==0)return false;
	}
	return true;
}
int main()
{
	for(int i=2;i<=10000;i++)
	{
		if(is_prime(i))
		{
			store_prime[cnt++]=i;
		}
	}
	int tmp,sum,n,ans;
	while(cin>>n)
	{
		ans=0;
		for(int i=0;i<cnt;i++)
		{
			for(int j=i;j<cnt;j++)
			{
				tmp=n-store_prime[i]-store_prime[j];
				if(tmp>=store_prime[j]&&is_prime(tmp))
				ans++;
			}
		}
		cout<<ans<<endl;
	}
	return 0;
}