POJ 2362/DFS:判断是否能形成正方形

1011简单改一下就OK了

#include <iostream>
#include <algorithm>
using namespace std;
#define MAX 64
int sticks[MAX];
bool used[MAX];
int stickNum,plen,n;

bool compare(int a, int b)
{
    return a > b;    
}
//从beginIndex号开始匹配，下一步要匹配matchLen的stick,在此之前已经匹配了hasMatch条stick
bool dfs(int beginIndex,int matchLen,int hasMatch){
	
	if(matchLen==0){
		hasMatch++;
			
		if(hasMatch==4){
		
			return true;
		}
		for(beginIndex=0;used[beginIndex];beginIndex++);
		used[beginIndex]=true;
		if(dfs(beginIndex+1,plen-sticks[beginIndex],hasMatch))return true;
		used[beginIndex]=false;
		return false;
	
	}else{
		if(beginIndex>n-1)return false;
		for(int i=beginIndex;i<n;i++){
			if(used[i])continue;
			if(sticks[i]>matchLen)continue;
			if(i>0&&sticks[i]==sticks[i-1]&&!used[i-1])continue;
			used[i]=true;
			if(dfs(i+1,matchLen-sticks[i],hasMatch))
				return true;
			used[i]=false;
		}
	
	}
	//
	return false;

}
int main(int argc, char* argv[])
{
	//freopen("i://in.txt","r",stdin);
	int sum = 0;
	bool ok ;
	int i,j;
	int c;
	scanf("%d",&c);
	for(j=0;j<c;j++){
		ok = false;
		scanf("%d",&n);
		sum=0;
		for( i=0;i<n;i++){
			scanf("%d",&sticks[i]);
			sum += sticks[i];
		}
		
		if(sum%4!=0){
			ok = false;
			
		}else{
			sort(sticks,sticks+n,compare);
			plen = sum/4;
			used[0]=true;
			if(dfs(0,plen-sticks[0],0)){
				ok = true;
			}
			//used[0]=false;
		}
		printf("%s\n",ok?"yes":"no");
		memset(used,false,sizeof(used));
	}
	return 0;
}