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

39

 

Sample Output

02

 

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;}