题解 | #合并区间#

import java.util.*;
/**
 * Definition for an interval.
 * public class Interval {
 *     int start;
 *     int end;
 *     Interval() { start = 0; end = 0; }
 *     Interval(int s, int e) { start = s; end = e; }
 * }
 */
public class Solution {
    public ArrayList<Interval> merge(ArrayList<Interval> intervals) {
        if (intervals == null || intervals.size() == 0) return new ArrayList<Interval>();
        intervals.sort(new AA());
        ArrayList<Interval> res = new ArrayList<>();
        Interval interval = intervals.get(0);
        for (int j = 1,k=0; j < intervals.size(); j++) {
            if (interval.end >= intervals.get(j).start) {
                interval.end = Math.max(intervals.get(j).end, interval.end);
            } else {
                res.add(new Interval(interval.start, intervals.get(j-1).end));
                interval.start = intervals.get(j).start;
                interval.end = intervals.get(j).end;
            }
        }
        res.add(interval);
        return res;
    }
    class AA implements Comparator<Interval> {

        @Override
        public int compare(Interval o1, Interval o2) {
            return o1.start - o2.start;
        }
    }
}