poj 2739 Sum of Consecutive Prime Numbers

求一个数能够被连续的素数的和组成有几种方法：

直接用暴力;

View Code

#include<iostream>

#include<cstdio>

#include<cstdlib>

#include<algorithm>

#include<cmath>

#include<cstring>

using namespace std;

int prime[2024],cnt,sum;

void Prime(  )

{

   bool hash[5024] = { 0 };

   int t = ( int )sqrt( 10000.0 ) + 1;  

   for( int i = 3 ; i <= t; i +=2 )

   {

       if( !hash[i>>1] ) 

       {

           int tt = i << 1;

           for( int j = i*i ; j <= 10000 ; j += tt )    

                hash[j>>1] = true;    

       }        

   }    

   cnt = 0;

   prime[cnt++] = 2;

   t = 10000/2;

   for( int i = 1 ; i <= t ; i ++ )

   {

        if( !hash[i] )

        {

           prime[cnt++] = ( i<<1 ) + 1;    

        }        

   }

}

int Research( int num )

{

    int i = cnt -1;

    int ans = 0;

    while( prime[i] > num )

           i--;

    for( ; i >= 0; i -- )

    {

       int sum = prime[i];

       int j = i -1;

       while( sum < num && j >=0 )

       {

             sum += prime[j];

             j --;

       }

       if( sum == num ) ans++;    

    }

    return ans;    

}

int main( )

{

    Prime();

    int n;

    while( scanf( "%d",&n ) ,n )

    {  

       printf( "%d\n",Research( n  ) );        

    }

   return 0;

}