Search for HDU 1518 Square

Square time limit: 10000/5000 ms (Java/other) memory limit: 65536/32768 K (Java/other) total submission (s): 11 accepted submission (s): 5 Font: times New Roman | verdana | georgiafont size: Drawing → problem descriptiongiven a set of sticks of various lengths, is it possible to join them end-to-end to form a square?
Inputthe first line of input contains N, the number of test cases. each test case begins with an integer 4 <= m <= 20, the number of sticks. M integers follow; each gives the length of a stick-an integer between 1 and 10,000.
Outputfor each case, output a line containing "yes" if is possible to form a square; otherwise output "no ".
Sample Input

34 1 1 1 15 10 20 30 40 508 1 7 2 6 4 4 3 5

Sample output

yesnoyes

#include<iostream>#include<cstring>using namespace std;int v[23],n,flag;int a[23],sum;void dfs(int p,int ans,int t){if(ans==sum/4){p++;if(p==4){flag=1;return ;}else ans=0;t=0;}if(flag)   return ;for(int i=t;i<n;i++)if(!v[i] && a[i]+ans<=sum/4){v[i]=1;dfs(p,ans+a[i],i);v[i]=0;}}int main(){int T;cin>>T;while(T--){cin>>n;int max;max=sum=0;for(int i=0;i<n;i++){cin>>a[i];sum += a[i];if(max<a[i])   max=a[i];}if(sum%4!=0 || max>sum/4)cout<<"no\n";else{memset(v,0,sizeof(v));flag=0;dfs(0,0,0);if(flag)   cout<<"yes\n";else     cout<<"no\n";}}return 0;}