java 代码

//右区间值大，就合并，然后更新右值
import java.io.*;
import java.lang.Integer;
import java.util.*;
class Node{
    int first;
    int second;
    public Node(int first, int second){
        this.first = first;
        this.second = second;
    }
}
class Main{
    public static void main(String[] args)throws Exception{
        BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.valueOf(buf.readLine());
        Node[] nodes = new Node[n];
        for(int i = 0; i < n; ++i){
            String[] params = buf.readLine().split(" ");
            int x = Integer.valueOf(params[0]);
            int y = Integer.valueOf(params[1]);
            nodes[i] = new Node(x, y);
        }
        Arrays.sort(nodes, (p,q)->{return p.first - q.first;});
        int cnt = 0;
        int max = Integer.MIN_VALUE;
        for(int i = 0; i < n; ++i){//只比较右值，包含在里面则合并，没包含则加1
            if(max < nodes[i].first)cnt++;
            max = Math.max(max, nodes[i].second);
        }
        System.out.printf("%d", cnt);
    }
}