JAVA 代码

import java.util.Scanner;
import java.util.Arrays;
public class Main{
    static int n;
    static int N = 200010; //2n
    static int[][] segs, res;
    static int segSize = 0; //统计segs区间的个数
    static int resSize = 0; //统计合并后区间的个数
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        //存放题目数组
        segs = new int[n][2];
        res = new int[n][2];
        //读
        for(int i = 0; i < n; i ++){
            segs[i][0] = sc.nextInt();
            segs[i][1] = sc.nextInt();
            segSize ++;
        }

        merge(segs);

        System.out.println(resSize);
    }

    public static void merge(int[][] segs){
        //排序
        Arrays.sort(segs, (o1, o2) -> o1[0] - o2[0]);
        //设置边界
        int start = Integer.MAX_VALUE, end = Integer.MIN_VALUE;
        int j = 0;
        //循环区间个数次
        for(int i = 0; i < segSize; i ++){
            //取每个区间左右端点
            int l = segs[i][0], r = segs[i][1];
            //判断两个区间有无交集
            if(end < l){
                //不是第一次更新的话，就将其存储
                if(start != Integer.MAX_VALUE){
                    res[j][0] = l;
                    res[j][1] = r;
                    j ++;
                    resSize ++;
                } 
                //更新过来
                start = l;
                end = r;
            }else{
                //有交集，合并
                end = Math.max(end, r);
            }
        }

        if(start != Integer.MAX_VALUE){
            res[j][0] = start;
            res[j][1] = end;
            resSize ++;
        } 
    }
}