题解 | #合并区间#

import java.util.*;

/*
 * public class Interval {
 *   int start;
 *   int end;
 *   public Interval(int start, int end) {
 *     this.start = start;
 *     this.end = end;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param intervals Interval类ArrayList
     * @return Interval类ArrayList
     */
    public ArrayList<Interval> merge (ArrayList<Interval> intervals) {
        if (intervals.size() == 1) {
            return intervals;
        }
        Collections.sort(intervals,new Comparator<Interval>(){
            public int compare(Interval i1,Interval i2){
                if(i1.start!=i2.start){
                    return i1.start-i2.start;
                }else{
                    return i1.end-i2.end;
                }
            }
        });
        // write code here
        //重载比较，按照区间首排序
        ArrayList<Interval> res=new ArrayList<>();
        for (int i = 0; i < intervals.size(); i++) {
            //最开始res里面数组为0
            int left=intervals.get(i).start; 
            int right=intervals.get(i).end;
            int size=res.size();
            if (size==0||res.get(size-1).end<left) {
                res.add(intervals.get(i));
            } else {
                Interval temp = new Interval(res.get(size-1).start, Math.max(res.get(size-1).end, right));
                res.remove(size-1);
                res.add(temp);
            }
        }
        return res;
    }

}