HDU5104-Primes Problem

Primes Problem

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 integern(n≤10000).

 

Output

For each test case, print the number of ways.

 

Sample Input

3

9

Sample Output

0

2

#include <bits/stdc++.h>///Primes Problemusing namespace std;#define N 10005int prime[N];int q[N];int main(){    int i,j,k,n,l=0,sum;    memset(q,0,sizeof(q));    prime[0]=0;    prime[1]=0;    prime[2]=1;    for(i=3;i<N;i++)//首先偶数一定不是素数,除了2    {        if(i%2)            prime[i]=1;        else            prime[i]=0;    }    for(i=3;i<=sqrt(N);i++)    {        if(prime[i])        for(j=i+i;j<N;j=j+i)//当i是素数的时候，i的所有的倍数必然是合数        prime[j]=0;    }    for(k=0;k<10000;k++)    {        if(prime[k])            q[l++]=k;    }    while(~scanf("%d",&n))    {        sum=0;        for(int i=0;q[i]<n;i++)            for(int j=i;q[j]<n-q[i];j++)            {                if(prime[n-q[i]-q[j]]&&n-q[i]-q[j]>=q[j])                {                    sum++;                }            }        printf("%d\n",sum);    }    return 0;}