学步园

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

class node implements Comparable
{
	public int start;
	public int end;
	public node(int x,int y)
	{
		this.start=x;
		this.end=y;
	}
	public int compareTo(Object obj)
	{
		if(obj instanceof node)
		{
			node bNode=(node)obj;
			if(this.end>bNode.end)
				return 1;
			else
			{
				return -1;
			}
		}
		return 0;
	}
}
public class Main {

	/**
	 * @param args
	 */
	static node nodes[];
	public static void main(String[] args) {
		// TODO Auto-generated method stub
     Scanner scanner=new Scanner(System.in);
     int time=scanner.nextInt();
     while(time--!=0)
     {
    	 int number=scanner.nextInt();
    	 nodes=new node[number];
    	 for(int i=0;i<number;i++)
    	 {
    		 int start,end;
    		 start=scanner.nextInt();
    		 end=scanner.nextInt();
    		 nodes[i]=new node(start, end);
    	 }
    	 Arrays.sort(nodes);
    	 int count=1;
    	 for(int j=1;j<number;j++)
    	 {
    		 if(nodes[0].end<nodes[j].start)
    		 {
    			 count++;
    			 nodes[0].end=nodes[j].end;
    		 }
    	 }
    	 System.out.println(count);
     }
	}

}

优先队列：

import java.util.PriorityQueue;
import java.util.Scanner;
class activity implements Comparable<activity>{
	
	int stime,etime;
    public activity(int stime, int etime) {
		this.stime = stime;
		this.etime = etime;
	}
	public int compareTo(activity atv) {
		if(atv instanceof activity)
		{
			if(this.etime>atv.etime)
				return 1;
			else return -1;
		}
		return -1;
	}
    
}
public class Main {
	static activity [] atvs;
	public static void main(String[] args) {
	Scanner scan=new Scanner(System.in);
	int times=scan.nextInt();
	PriorityQueue<activity> pQueue=new PriorityQueue<activity>();
	while(times--!=0)
	{
		int activities=scan.nextInt();
		atvs=new activity[activities];
		for(int i=0;i<activities;i++)
		{
			atvs[i]=new activity(scan.nextInt(), scan.nextInt());
			pQueue.add(atvs[i]);
		}
		int number=1;
		int top=pQueue.poll().etime;
		for(int i=1;i<activities;i++)
		{
			if(top<pQueue.peek().stime)
			{
				top=pQueue.peek().etime;
				number++;
			}
			pQueue.poll();
		}
		pQueue.clear();
		System.out.println(number);
		
	}
  }
}