【Leetcode】Merge Intervals

Given a collection of intervals, merge all overlapping intervals.

For example,
Given [1,3],[2,6],[8,10],[15,18],
return [1,6],[8,10],[15,18].

Java:

1. http://blog.youkuaiyun.com/linhuanmars/article/details/21857617

2. 备用：http://blog.youkuaiyun.com/fightforyourdream/article/details/16882295

熟悉下自建 Comparator 还比较清晰易懂

/**
 * 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 intervals;
        ArrayList<Interval> res= new ArrayList<Interval>();
        Comparator<Interval> comp=new Comparator<Interval>(){
            @Override
            public int compare(Interval i1,Interval i2)
            {
                if(i1.start==i2.start) return i1.end-i2.end;
                return i1.start-i2.start;
            }
        };
        Collections.sort(intervals, comp);
        res.add(intervals.get(0));
        for(int i=1;i<intervals.size();i++)
        {
            if(res.get(res.size()-1).end>=intervals.get(i).start)
            {
                res.get(res.size()-1).end=Math.max(res.get(res.size()-1).end, intervals.get(i).end);
            }
            else{
                res.add(intervals.get(i));
            }
        }
        return res;
    }
}