HDU 5104 Primes Problem（素数打表）

Primes Problem

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3614 Accepted Submission(s): 1629

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 Input39Sample Output02

题目不难，就是先打表在暴力，直接暴力不用想肯定超。

#include<iostream>#include<algorithm>#include<cstdio>#include<cstring>using namespace std;int pr[10010],bo[100000]={0};int num=0;void primes(){    for (int i=2;i<=10000;i++)    {        if(!bo[i])            pr[++num]=i;        for (int j=1;j<=num && pr[j]*i<=10000;j++)        {            bo[i*pr[j]]=1;            if(i%pr[j]==0)break;        }    }}int main(){    primes();    int k,n,m,sum;    while(scanf("%d",&k)!=EOF)    {        sum=0;        for(int i=1;pr[i]<=k;i++)        {            for(int j=i;pr[j]<=k;j++)            {                if(!bo[k-pr[i]-pr[j]]&&(k-pr[i]-pr[j])>=pr[j])                    sum++;            }        }       printf("%d\n",sum);    }    return 0;}