poj 2362 Square

#include <iostream>            //参照poj 1011 sticks
#include <algorithm>
using namespace std;
int sticks[20],visited[20];
int flag,total;
int t,seg;
int cmp(const void* a,const void* b)
{
    return (*(const int*)b)-(*(const int *)a);
}
void solve(int k,int sum,int cnt)   
{
    if(cnt==4)
        flag=true;
    else if(sum==seg)
        solve(0,0,cnt+1);        
    else    
        for (int pre=-1,i=k;i<t;++i)    
            if(visited[i]!=1&&sticks[i]!=pre&&sticks[i]+sum<=seg)        
            {
                pre=sticks[i];
                visited[i]=1;
                solve(i+1,sum+sticks[i],cnt);    
                visited[i]=0;        
                
                if(k==0||flag==1)return;    
            }
}
int main()
{
    int c,i;
    scanf("%d",&c);
    while(c--)
    {
        total=0;
        flag=0;
        scanf("%d",&t);
        for (i=0;i<t;++i)
        {
            scanf("%d",&sticks[i]);
            total+=sticks[i];      
        }
        
        qsort(sticks,t,sizeof(sticks[0]),cmp);            
        if(total%4!=0||sticks[0]>total/4)
            printf("no\n");
        else
        {
            seg=total/4;
            memset(visited,0,sizeof(visited));
            solve(0,0,0);
            if(flag)
                printf("yes\n");
            else
                printf("no\n");
        }
    }
    return 0;
}