POJ2362:Square

#include<stdio.h>#include<string.h>#include<algorithm>using namespace std;int a[250],len,r[205],n,sum;int dfs(int p,int q,int z){ if(p==3) return 1;int j;for(j=q;j>=0;j--){if(!r[j]){r[j]=1;if(z+a[j]<len){if(dfs(p,j-1,z+a[j]))return 1;}else if(z+a[j]==len){if(dfs(p+1,n-1,0))return 1;}r[j]=0;} }return 0;  }int main(){int i,k,m;scanf("%d",&m);while(m--){sum=0;scanf("%d",&n);for(i=0;i<n;sum+=a[i],i++)scanf("%d",&a[i]);len=sum/4;memset(r,0,sizeof(r));sort(a,a+n);if(len*4!=sum || len<a[n-1]){              printf("no\n");              continue;          }          if(dfs(0,n-1,0))              printf("yes\n");          else              printf("no\n");      }  return 0;}