leetcode题解（二十六）：56. Merge Intervals

题意：重叠的interval可以合并在一起
Example 1:

Input: [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6].

Example 2:

Input: [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] are considered overlapping.

public List<Interval> merge(List<Interval> intervals) {
	//考虑边界情况
    if (intervals.size() <= 1)
        return intervals;
    
    // Sort by ascending starting point using an anonymous Comparator
    intervals.sort((i1, i2) -> Integer.compare(i1.start, i2.start));
    List<Interval> result = new LinkedList<Interval>();
    
    //拿到第一个interval的开始和结尾
    int start = intervals.get(0).start;
    int end = intervals.get(0).end;
    
    for (Interval interval : intervals) {
    	//比较当前interval和上一次end的大小，如果有重叠
        if (interval.start <= end) // Overlapping intervals, move the end if needed
        	//更新end
            end = Math.max(end, interval.end);
        //没有重叠的话
        else {                     // Disjoint intervals, add the previous one and reset bounds
        	//result中直接加入上一次的start 和 end
            result.add(new Interval(start, end));
            //更新start 和 end
            start = interval.start;
            end = interval.end;
        }
    }
    
    // Add the last interval
    result.add(new Interval(start, end));
    return result;
}