LeetCode 56 Merge Intervals

原题:（频率5）

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].

题意：给一个intervals的集合，合并所有重叠的。

代码和思路：

/**
 * 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()<=1){
            return intervals;
        }
        //按start大小排序
        intervals.sort((i1, i2) -> Integer.compare(i1.start, i2.start));
        
        List<Interval> result = new LinkedList<>();
        
        int start = intervals.get(0).start;
        int end = intervals.get(0).end;
        
        for(Interval i:intervals){
            if(i.start <= end){
                end = Math.max(end,i.end);
            }
            else{
                result.add(new Interval(start,end));
                start = i.start;
                end = i.end;
            }
        }
        //因为循环中会漏加最后一组，这里加上
        result.add(new Interval(start,end));
        return result;
    }
}