HDU 5339 Untitled(暴搜)

 

　　　　　　　　　　　　　　　　　Untitled

 

Problem Description
There is an integer a and n integers b1,…,bn. After selecting some numbers from b1,…,bn in any order, say c1,…,cr, we want to make sure that a mod c1 mod c2 mod… mod cr=0 (i.e., a will become the remainder divided by ci each time, and at the end, we want a to become 0). Please determine the minimum value of r. If the goal cannot be achieved, print −1 instead.

 

Input
The first line contains one integer T≤5, which represents the number of testcases.

For each testcase, there are two lines:

1. The first line contains two integers n and a (1≤n≤20,1≤a≤106).

2. The second line contains n integers b1,…,bn (∀1≤i≤n,1≤bi≤106).

 

Output
Print T answers in T lines.

 

Sample Input
2
2 9
2 7
2 9
6 7

 

Sample Output
2
-1

 

 

 

#include<cstdio>
#include<algorithm>
using namespace std;

int ans,m,n;
int b[21];

bool cmp(int a,int b)
{
    return a>b;
}

void dfs(int total,int cur,int num)
{
    if(total==0)
    {
        ans=min(ans,num);
        return;
    }
    if(cur==m)
    return;
    dfs(total%b[cur],cur+1,num+1);
    dfs(total,cur+1,num);
}

int main()
{
    //freopen("in.txt","r",stdin);
    int i,t;
    scanf("%d",&t);
    while(t--)
    {
        ans=21;
        scanf("%d%d",&m,&n);
        for(i=0;i<m;i++)
        scanf("%d",&b[i]);
        sort(b,b+m,cmp);
        dfs(n,0,0);
        if(ans==21)
        printf("-1\n");
        else
        printf("%d\n",ans);
    }
    return 0;
}