poj2362

这道题和1011十分类似。只要把所有木棒分为4份即可。

#include<iostream>
#include<fstream>
#include<algorithm>
#include<string.h>
using namespace std;
int n;
const int NUM=20;
bool visited[NUM];
int stick[NUM];
int des_len;
int cmp(const void* a,const void *b)
{
   return ( *(int *)b-*(int *)a);
}
bool search(int len,int s,int num)
{
	if(num==4)
		return true;
	int last=-1;
	for(int i=s;i<n;i++)
	{
		if(visited[i]||stick[i]==last)
			continue;
		visited[i]=true;
		if(len+stick[i]<des_len)
		{
			if(search(len+stick[i],i+1,num))
				return true;
		}
		else if(len+stick[i]==des_len)
		{
			if(search(0,0,num+1))
					return true;
		}
		visited[i]=false;
		last=stick[i];
		if(len==0)
		return false;
	}
	return false;
}
int main()
{
	freopen("input.txt","r",stdin);
        int N;
	cin>>N;
	while(N--)
	{
		cin>>n;
		memset(visited,false,sizeof(bool)*NUM);
		int sum_len=0; 
		for(int i=0;i<n;i++)
		{
			cin>>stick[i];
			sum_len+=stick[i];
		}
		qsort(stick,n,sizeof(int),cmp);
                des_len=sum_len/4;
		if(des_len*4==sum_len&&search(0,0,0))
			cout<<"yes"<<endl;
		else
			cout<<"no"<<endl;
	}
	return 0;
}