hdu 1518 深搜

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
int len[22],n,El;
int vi[22];
int dfs(int k,int pos,int nowlen)
{
    int i,j;
    if(nowlen==El)
    {
        if(k==n)
            return 1;
        else
            nowlen=0,pos=0;
    }
    for(i=pos;i<n;i++)
    {
        if(!vi[i]&&nowlen+len[i]<=El)
        {
            vi[i]=1;
            if(dfs(k+1,i+1,nowlen+len[i]))
                return 1;
            vi[i]=0;
        }
    }
    return 0;
}
int main()
{
    int t,i,j,Max,sum=0;;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        Max=0,sum=0;
        memset(vi,0,sizeof(vi));
        for(i=0;i<n;i++)
        {
            scanf("%d",&len[i]);
            if(len[i]>Max)
                Max=len[i];
            sum+=len[i];
        }
        El=sum/4;
        if(El*4!=sum||Max>El)
        {
            printf("no\n");
            continue;
        }
        if(dfs(0,0,0))
            printf("yes\n");
        else
            printf("no\n");
    }
    return 0;
}