Merge Intervals

题目描述：
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].

先将给定的intervals排序，然后从第一个开始，逐个比较，插入前面的interval，所以这个时候一定要注意最后一个interval，要单独拿出来讨论

public List<Interval> merge(List<Interval> intervals) {
    List<Interval> list=new ArrayList<Interval>();
    int n=intervals.size();
    if(n<=1)
        return intervals;
    intervals.sort((o1,o2)->{ if(o1.start>o2.start||(o1.start==o2.start&&o1.end>o2.end)) return 1; else if(o1.start<o2.start||(o1.start==o2.start&&o1.end<o2.end)) return -1; else return 0; }); Interval lastInterval=intervals.get(0); for (int i = 1; i < n; i++) { if(intervals.get(i).start>lastInterval.end){ list.add(lastInterval); lastInterval=intervals.get(i); }else{ lastInterval.end=lastInterval.end>intervals.get(i).end?lastInterval.end:intervals.get(i).end; } } //单独讨论最后一个interval if(intervals.get(n-1).start>lastInterval.end){ list.add(intervals.get(n-1)); }else{ list.add(lastInterval); } return list; }