POJ 2739. Sum of Consecutive Prime Numbers

Sum of Consecutive Prime Numbers

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 20050		Accepted: 10989

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

来源： <http://poj.org/problem?id=2739>

 

简单打表水题，往下写之前先看看 10000 内的素数有多少个，然后就可以开数组给OJ生成了，或者自己复制粘贴好数组交上去。

得到数组就可以对数组进行游标法遍历了，不难。甚至试除法都可以过= =

 

#include <stdio.h>
#include <math.h>
int pr[1229];
int ispr(int n)
{
    int p=sqrt(n);
    for(int i=2;i<=p;i++)
        if(n%i==0) return 0;
    return 1;
}
int main()
{
    int n,cnt=0;
    int i,j,c;
    long sum;

    for(i=2;i<=10000;i++)
        if(ispr(i))
            pr[cnt++]=i;

    while(~scanf("%d",&n)&&n)
    {
        c=0;
        for(i=0;i<cnt&&pr[i]<=n;i++)
        {
            sum=0;
            for(j=i;j<cnt;j++)
            {
                sum+=pr[j];
                if(sum>=n) break;
            }
            if(sum==n) c++;
        }
        printf("%d\n",c);
    }
    return 0;
}

 

By Black Storm（使用为知笔记）