题解 | #合并区间#

排序

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; }
 * }
 */
class MyComparator implements Comparator<Interval> {
    @Override
    public int compare(Interval o1, Interval o2) {
        return Integer.compare(o1.end, o2.end);
    }
}

public class Solution {
    public ArrayList<Interval> merge(ArrayList<Interval> intervals) {
        if (intervals.size() <= 1) {
            return intervals;
        }
        Comparator cmp = new MyComparator();
        Interval[] objs = intervals.toArray(new Interval[0]);
        Arrays.sort(objs, cmp);

        ArrayList<Interval> result = new ArrayList<>();
        Interval obj = objs[objs.length-1];
        for(int i = objs.length-2; i >= 0; i--) {
            if (obj.start <= objs[i].end) {
                if (obj.start > objs[i].start) {
                    obj.start = objs[i].start;
                }
            } else {
                result.add(obj);
                obj = objs[i];
            }
            if (i == 0) {
                result.add(obj);
            }
        }
        Collections.reverse(result);
        return result;
    }
}