leetcode 56. Merge Intervals

Given a collection of intervals, merge all overlapping intervals.

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.

 

第一次用java自带的“List” 这个数据结构，好多用法还不清楚，尤其是sort这个自带的排序方法....

/**
 * 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 Solution {
    public List<Interval> merge(List<Interval> intervals) {
        if(intervals.size() < 2) return intervals;
        
        // Sort by ascending starting point using an anonymous Comparator
        intervals.sort((i1,i2) -> Integer.compare(i1.start,i2.start));
        int start = intervals.get(0).start;
        int end = intervals.get(0).end;
        
        List<Interval> x = new LinkedList<Interval>();
        for(Interval interval: intervals) {
            if(interval.start <= end) {
                end = Math.max(end, interval.end);
            }else{
                x.add(new Interval(start,end));
                start = interval.start;
                end = interval.end;
            }
        }
        
        //add the last interval;
        x.add(new Interval(start,end));
        return x;
    }
}