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.

/**
 * 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) {
        Collections.sort(intervals,new Comparator<Interval>(){  
            public int compare(Interval int1,Interval int2){
                return int1.start - int2.start ;
            }
        });
        if(intervals.size()<2) return intervals;
        List<Interval> res = new ArrayList<Interval>();
        Interval inte = intervals.get(0);
        for(int i = 0 ;i<intervals.size();i++){
            Interval temp = intervals.get(i);
            if(inte.end>=temp.start){
                inte.end = Math.max(inte.end,temp.end);
            }else
            {
                res.add(inte);
                inte = temp;
            }
        }
        res.add(inte);
        return res;
    }
}