hoj1956 square

/*This Code is Submitted by billforum for Problem 1956 at 2012-01-31 17:30:00*/
#include <iostream>
#include <algorithm>

using namespace std;

struct point
{
int num;
int next;
};
point data[100];
bool visit[100];
int total,len,n;

bool cmp(point x,point y)
{
return (x.num>y.num);
}

bool dfs(int res,int next,int cpl)
{

if(res==len)
{
res=0;
cpl++;
next=1;
}
if(cpl==total) return true;
int i=next;

while(i<n)
{
if(visit[i])
{
i++;
continue;
}//if
if(data[i].num+res<=len)
{
visit[i]=1;
if(dfs(data[i].num+res,i+1,cpl)) return true;
visit[i]=0;//
if(res==0) break;//剪枝
if(res+data[i].num==len) break;//剪枝
i=data[i].next;
continue;
}//if
i++;
}//while
return false;
}

int main(int args,char** argv)
{
int ind,id,sum,test,flag;
cin>>test;
while(test--)
{
sum=0;
flag=0;
cin>>n;
for(int i=0;i<n;i++)
{
cin>>ind;
data[i].num=ind;
sum+=ind;
visit[i]=0;
}
sort(data,data+n,cmp);
id=0;
while(id<n)
{
int j=id+1;
while((data[j].num==data[id].num)&&j<n) j++;//j?=n
for(int i=id;i<j;i++)
data[i].next=j;
id=j;
}//while
if(sum%4==0)
{
len=sum/4;
total=4;
if(dfs(0,0,0)) flag=1;

}
if(flag==0) cout<<"no"<<endl;
else cout<<"yes"<<endl;

}//while

return 0;
}