[LeetCode] Insert Interval

Problem:

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

You may assume that the intervals were initially sorted according to their start times.

Example 1:
Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9].

Example 2:
Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as [1,2],[3,10],[12,16].

This is because the new interval [4,9] overlaps with [3,5],[6,7],[8,10].

Solution:O(n)

public class Solution {
    public ArrayList insert(ArrayList intervals, Interval newInterval) {
        ArrayList list= new ArrayList();
        for(Interval interval: intervals){
            if(interval.end < newInterval.start){
                list.add(interval);
            }else if(interval.start > newInterval.end){
                list.add(newInterval);
                newInterval = interval;        
            }else if(interval.end >= newInterval.start || 

                interval.start <= newInterval.end){
                newInterval = new Interval(Math.min(interval.start, newInterval.start), Math.max(newInterval.end, interval.end));
            }
        }
        list.add(newInterval); 
        return list;
    }
}

Key concept: consider three cases