poj 2739（筛法求素数）

　　Sum of Consecutive Prime Numbers

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 21613		Accepted: 11837

Description

Some positive integers can be represented by a sum of one or more consecutive prime numbers. How many such representations does a given positive integer have? For example, the integer 53 has two representations 5 + 7 + 11 + 13 + 17 and 53. The integer 41 has three representations 2+3+5+7+11+13, 11+13+17, and 41. The integer 3 has only one representation, which is 3. The integer 20 has no such representations. Note that summands must be consecutive prime
numbers, so neither 7 + 13 nor 3 + 5 + 5 + 7 is a valid representation for the integer 20.

Your mission is to write a program that reports the number of representations for the given positive integer.

Input

The
input is a sequence of positive integers each in a separate line. The
integers are between 2 and 10 000, inclusive. The end of the input is
indicated by a zero.

Output

The
output should be composed of lines each corresponding to an input line
except the last zero. An output line includes the number of
representations for the input integer as the sum of one or more
consecutive prime numbers. No other characters should be inserted in the
output.

Sample Input

2
3
17
41
20
666
12
53
0

Sample Output

1
1
2
3
0
0
1
2

Source

Japan 2005

 

心得：第一个循环a写成了n；T半天；选择循环时优先选择短的那条；

 #include<iostream>
 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 #include<cstdlib>
 #include<cmath>
 #include<vector>
 #include<queue>
 #include<stack>
 using namespace std;
 #define N 10000
 int n,m,pr[N],a=;
 bool p[N];
 void gcd(){
     for(int i=;i<N;i++){
         if(!p[i]){ pr[a++]=i;}
         for(int j=i*i;j<N;j+=i)
             p[j]=true;
     }
 }

 int main(){
    //freopen("in.txt","r",stdin);
      memset(p,false,sizeof(p));
     gcd();
     while(cin>>n,n){
         int j=,sum;m=;
         for(int i=;i<a;i++){
                 sum=;j=i;
             while(sum<n){
                 sum+=pr[j++];
             }
             if(sum==n)
                 m++;
         }
         printf("%d\n",m);
     }
     return ;
 }