区间选点 ===== java 题解

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

class Range{
    public int l,r;
    public Range(int l,int r){
        this.l = l;
        this.r = r;
    }
    @Override
    public String toString() {
        return "Range [l=" + l  + ", r=" + r + "]";
    }

}
public class Main {
    static int N = 100010;
    static int n;
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        Range []ranges = new Range[n];
        for (int i= 0; i < ranges.length; i++){
            ranges[i] = new Range(0,0);
        }


        for(int i = 0; i < n; i++){
            int xl = sc.nextInt();
            int xr = sc.nextInt();
            ranges[i] = new Range(xl,xr);
        }
        //实现排序接口
        Comparator<Range> cmp = new Comparator<Range>() {
            @Override
            public int compare(Range o1, Range o2) {
                if(o1.r < o2.r){
                    return -1;
                }else if(o1.r > o2.r){
                    return 1;
                }else{
                    return 0;
                }
            }
        };

        Arrays.sort(ranges,cmp);

        int res = 0;
        double ed = -2e9;
        for(int i = 0; i < n; i++){
            if(ranges[i].l > ed){
                res++;
                ed = ranges[i].r;
            }
        }
        System.out.println(res);

    }
}