HDU 2098 split primes and number theory

Split Prime andTime limit:1000MS Memory Limit:32768KB 64bit IO Format:%i64d &%i64 U

Description

To split an even number into two different prime numbers, how many methods are there?

Input

The input contains some positive even numbers, the value will not exceed 10000, the number will not exceed 500, if in the event of 0, the end.

Output

corresponding to each even, the output is split into the number of different primes, each result occupies a row.

Sample Input

30 26 0

Sample Output

3 2 The key is to do a pre-treatment

#include <iostream> #include <cstring> #include <cstdio> #include <algorithm> #include < queue> #include <vector> #include <iomanip> #include <math.h>using namespace std; #define FIN     Freopen ("Input.txt", "R", stdin), #define INF     0x3f3f3f3f#define lson l,m,rt<<1#define rson    m+1,r, Rt<<1|1typedef Long Long Ll;int p[10005];int s[5005];int main () {    //fin    int cas=0;    for (int i=2, i<=10000; i++)    {        if (p[i]==0)        {for            (int j=i+i; j<=10000; j=j+i)            {                p[j]= 1    ;    }}} for (int i=2; i<=10000; i++)    {        if (p[i]==0)            s[cas++]=i;    }    int n;    while (~SCANF ("%d", &n) &&n)    {        int cnt=0;        for (int i=3; i<n/2; i+=2)        {            if (!p[i]&&!p[n-i])                cnt++;        }        printf ("%d\n", CNT);    }}

　　

HDU 2098 split primes and number theory