HDU 1518 Square

Square

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>

using namespace std;

int T,n,sum,len;
int info[25];
bool v[25],flag;

int dfs(int id,int completed,int length){
if(completed==4)return 1;
for(int i=id;i<=n;i++){
if(!v[i]){
if(length-info[i]==0){
v[i]=1;
if(dfs(1,completed+1,len)) return 1;
v[i]=0;
}
else if(length-info[i]>0){
v[i]=1;
if(dfs(i+1,completed,length-info[i])) return 1;
v[i]=0;
}
}
}
return 0;
}

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

int main(){
cin>>T;
while(T--){
sum = 0;
scanf("%d",&n);
for(int i=1;i<=n;i++){
scanf("%d",info + i);
sum+=info[i];
}
sort(info+1,info+1+n,cmp);
if(sum%4||n<4){
puts("no");
continue;
}
len = sum/4;
memset(v,0,sizeof(v));
if(dfs(0,0,len))    puts("yes");
else    puts("no");
}
return 0;
}