Xinshoucun - procedure function and recursive -P1036 election

Description Title
known n integers x1, x2, ..., xn, and an integer k (k <n). Optionally adding integers k from n integers in a range of available respectively. For example, when n = 4, k = 3,4 are integers when 3,7,12,19, available with all combinations thereof and is:

3＋7＋12=22

3＋7＋19＝29

7＋12＋19＝38

3＋12＋19＝34。

Now, we ask you to calculate the total number of species and is a prime number.

For example the embodiment, only one, and is a prime number: 3 + 7 + 19 = 29).

Input and output format
input format:

Keyboard input format:

n , k （1<=n<=20，k＜n）

x1,x2，…,xn （1<=xi<=5000000）

Output formats:

Screen output format:

An integer (satisfy several criteria).

Input Output Sample
Input Sample # 1:

4 3
3 7 12 19

Output Sample # 1:

1
----------------
idea: DFS search then determines whether or not a prime number and satisfy several conditions is +1

#include<cstdio>
#include<cmath>
#include<iostream>
using namespace std;
int a[10001];
int n,k,sum,tot;

inline bool prime(int x)  
    {
        for(register int i=2;i*i<=x;i++)
            if(x%i==0)
                return false;
        return true;
    }
   
inline void dfs(int step,int s,int count)
{
	if(step==n+1 || count == k)
	{
	 if(prime(s)&& count == k)	
	    tot++;
	    return;
	}
    dfs(step+1,s+a[step],count+1);
    dfs(step+1,s,count);
     return;
}

inline void print(){
	printf("%d",tot);
}
int main(){
	scanf("%d %d",&n,&k);
	for(register int i=1;i<=n;i++)
	scanf("%d",&a[i]);
	dfs(1,0,0);
	print(); 
	return 0;
}