Square_hdu_1518(深搜)

Square
Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 5868 Accepted Submission(s): 1869

Problem Description
Given a set of sticks of various lengths, is it possible to join them end-to-end to form a square

Input
The 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.

Output
For each case, output a line containing "yes" if is is possible to form a square; otherwise output "no".

Sample Input
3
4 1 1 1 1
5 10 20 30 40 50
8 1 7 2 6 4 4 3 5

Sample Output
yes
no
yes

Source
University of Waterloo Local Contest 2002.09.21

import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;

public class Main{//8855163	2013-08-07 11:15:44	Accepted	1518	968MS	3940K	1278 B	Java	zhangyi
	private static boolean vis[],ok=true;
	private static Integer a[],sum=0,n;
	public static void main(String[] args) {
		Scanner input=new Scanner(System.in);
		int N=input.nextInt();
		while(N-->0){
			n=input.nextInt();
			Init();
			int max=0;
			for(int i=0;i>2;
			Arrays.sort(a,new Comparator(){    //从大到小排序
                @Override
                public int compare(Integer o1, Integer o2){
                    return o2-o1;
                }
            });
			if(max%4==0&&sum>=a[0]){
				dfs(0,0,0);//当时少了一个参数，导致超时
				if(ok)
					System.out.println("yes");
				else
					System.out.println("no");
			}
			else{
				System.out.println("no");
			}
		}
	}
	private static void Init() {
		sum=0;
		ok=false;
		a=new Integer[n];
		vis=new boolean[n];
	}
	private static void dfs(int s, int num,int i) {//一定要加i，否则会超时，下次直接从i处搜
		if(ok)
			return;
		if(num==3){
			ok=true;
			return;
		}
		if(s==sum){
			dfs(0,num+1,num+1);
		}
		for(;i 
 
import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;

public class Main{//1508MS
	static boolean vis[];
	static Integer a[],arge=0;
	public static void main(String[] args) {
		Scanner input=new Scanner(System.in);
		int N=input.nextInt();
		while(N-->0){
			int n=input.nextInt();
			a=new Integer[n];
			vis=new boolean[n];
			int sum=0;
			for(int i=0;i>2;
			if(sum%4==0){
				Arrays.sort(a,new Comparator(){

					@Override
					public int compare(Integer o1, Integer o2) {
						return o2-o1;
					}
					
				});
				if(arge>=a[0]&&dfs(0,0,0)){
					System.out.println("yes");
				}
				else
					System.out.println("no");
			}
			else{
				System.out.println("no");
			}
		}
	}
	private static boolean dfs(int len, int num, int i) {
		if(num==3)
			return true;
		if(len==arge){
			if(dfs(0,num+1,num+1))
				return true;
			else
				return false;
		}
		else{
			for(;i