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.isEmpty()){
            return intervals;
        }
        Collections.sort(intervals, new Comparator<Interval>() {
            @Override
            public int compare(Interval o1, Interval o2) {

                if (o1.start > o2.start) {
                    return 1;
                } else if (o1.start == o2.start) {
                    if (o1.end > o2.end) {
                        return 1;
                    } else {
                        return -1;
                    }
                } else {
                    return  -1;
                }
            }
        });
        ArrayList<Interval> result = new ArrayList<Interval>();
        result.add(intervals.get(0));
        for (int i = 1; i < intervals.size(); i++) {
            Interval interval = result.get(result.size() - 1);
            Interval interval1 = intervals.get(i);
            if (interval.end < interval1.start) {
                result.add(interval1);
            } else {
               interval.end = Math.max(interval1.end, interval.end);
            }
        }
        return result;
    }
}