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;

}