java 超时代码

import java.io.*;
import java.lang.*;
import java.util.*;

class Main{

    static int n = 0, N = 100010;
    static int[] groups = new int[N];
    static int group = 0;
    public static void main(String[] args)throws Exception{
        BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));
        n = Integer.valueOf(buf.readLine());
        int[][] nums = new int[n][2];
        int t = 0;
        while(n-- != 0){
            String[] info = buf.readLine().split(" ");
            int a = Integer.valueOf(info[0]);
            int b = Integer.valueOf(info[1]);
            nums[t][0] = a;
            nums[t][1] = b;
            t++;
        }
        Arrays.fill(groups, -0x3f3f3f3f);
        Arrays.sort(nums, (a,b)->{return a[0] - b[0];});//排序
        for(int i = 0; i < t; ++i){
            boolean flag = false;
            for(int j = 0; j <= group; ++j){
                if(nums[i][0] > groups[j]){
                    flag = true;
                    groups[j] = nums[i][1];
                    break;
                }
            }
            if(!flag)groups[++group] = nums[i][1];
        }

        System.out.print(group + 1);

    }
}

java 小根堆优化代码

import java.io.*;
import java.lang.*;
import java.util.*;

class Main{

    static int n = 0, N = 100010;
    static PriorityQueue<Integer> qu = new PriorityQueue<>();
    public static void main(String[] args)throws Exception{
        BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));
        n = Integer.valueOf(buf.readLine());
        int[][] nums = new int[n][2];
        int t = 0;
        while(n-- != 0){
            String[] info = buf.readLine().split(" ");
            int a = Integer.valueOf(info[0]);
            int b = Integer.valueOf(info[1]);
            nums[t][0] = a;
            nums[t][1] = b;
            t++;
        }
        Arrays.sort(nums, (a,b)->{return a[0] - b[0];});//排序
        for(int i = 0; i < t; ++i){
            if(qu.isEmpty() || qu.peek() >= nums[i][0]){
                qu.offer(nums[i][1]);
            }else if(qu.peek() < nums[i][0]){
                qu.poll();
                qu.offer(nums[i][1]);
            }
        }
        System.out.print(qu.size());

    }
}