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) {
        // write code here
        ArrayList<Interval> list = new ArrayList<>();
        if (intervals.size() <= 1) return intervals;
        Collections.sort(intervals, new Comparator<Interval>() {
            public int compare(Interval a, Interval b) {
                return a.start - b.start;
            }
        });

        
        int start = intervals.get(0).start;
        int end = intervals.get(0).end;

        for (int i=1; i<intervals.size(); i++) {
            Interval it = intervals.get(i);
            if (it.start > end) {
                list.add(new Interval(start, end));
                start = it.start;
                end = it.end;
            } else {
                if (it.end >= end) {
                    end = it.end;
                }
            }
        }
        list.add(new Interval(start, end));
        return list;
    }
}