LeetCode-56 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].

 

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思路：

1.先将输入集合按照start大小排序，对集合的排序可以利用Collections.sort()方法，并实现Comparator<T>接口。

2.对排好序的集合进行合并

代码如下：

public List<Interval> merge(List<Interval> intervals) {
        if(intervals == null || intervals.size() < 2)
            return intervals;
        Collections.sort(intervals, new Comparator<Interval>() {
            @Override
            public int compare(Interval o1, Interval o2) {
                return o1.start - o2.start;
            }
        });
        
        List<Interval> list = new ArrayList<Interval>();
        list.add(intervals.get(0));
        for(int i=1; i<intervals.size(); i++) {
            Interval current = intervals.get(i);
            Interval result = list.get(list.size()-1);
            if(current.start > result.end) {
                list.add(current);
            } else if(current.end > result.end) {
                list.remove(list.size()-1);
                list.add(new Interval(result.start, current.end));
            }
        }
        return list;
    }