Loop Solution - Merge Intervals - sort involved *

The idea is to create new interval start and begin by loop using a cur which is initialized to be the first element. A merge sort is called to sort the inputs first.


/**
 * 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; }
 * }
 */
public class Solution {
    public ArrayList<Interval> merge(ArrayList<Interval> intervals) {
        if(intervals == null){
            return new ArrayList<Interval>();
        }
        if(intervals.size() < 2){
            return intervals;
        }
        ArrayList<Interval> clone = sort(intervals);
        intervals.clear();
        intervals.addAll(clone);
        ArrayList<Interval> res = new ArrayList<Interval>();
        Interval cur = intervals.get(0);
        int beginNewInterval = cur.start;
        int endNewInterval = cur.end;
        for(int i = 1; i < intervals.size(); i++){
            if(cur.end >= intervals.get(i).start){
                beginNewInterval = cur.start;
                endNewInterval = Math.max(cur.end, intervals.get(i).end);
                cur = new Interval(beginNewInterval, endNewInterval);
            }else{
                res.add(cur);
                cur = intervals.get(i);
            }
        }
        res.add(cur);
        return res;
    }
   
    private ArrayList<Interval> sort(ArrayList<Interval> inputs){  //!!!quick sort woule be better for space reason!!!
        if(inputs.size() < 2){
            return inputs;
        }
        int size = inputs.size();
        ArrayList<Interval> leftList = new ArrayList<Interval>(size/2);
    ArrayList<Interval> rightList = new ArrayList<Interval>(size - size/2);
for(int i = 0; i < size/2; i++){
leftList.add(i, inputs.get(i));
}
for(int i = 0; i < (size - size/2); i++){
rightList.add(i, inputs.get(i + size/2));
}
        return mergeS(sort(leftList), sort(rightList));
    }
   
    private ArrayList<Interval> mergeS(ArrayList<Interval> left, ArrayList<Interval> right){
        ArrayList<Interval> result = new ArrayList<Interval>();
        int leftIndex = 0;
        int rightIndex = 0;
        while(leftIndex < left.size() && rightIndex < right.size()){
            if(left.get(leftIndex).start < right.get(rightIndex).start){
                result.add(left.get(leftIndex));
                leftIndex++;
            }else{
                result.add(right.get(rightIndex));
                rightIndex++;
            }
        }
        while(leftIndex < left.size()){
            result.add(left.get(leftIndex));
            leftIndex++;
        }
        while(rightIndex < right.size()){
            result.add(right.get(rightIndex));
                rightIndex++;
        }
        return result;
    }
}