MergeIntervals.java

/**
 * 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 MergeIntervals {
	public List<Interval> merge(List<Interval> intervals) {
		
        if (intervals.size() < 0) {
			return null;
		}
        
        // meetings need not be sorted by time, do cleanup and sort by start time
        Collections.sort(intervals, new Comparator<Interval>(){
          public int compare(Interval a, Interval b){
              return a.start - b.start;
          }
        });
        
        // iterate the loop only till last but one element as we are doing i+1 in logic
		for (int i = 0; i < intervals.size() - 1; i++) {
			if (intervals.get(i).end >= intervals.get(i + 1).start) {
				intervals.get(i).end = getValidEnd(intervals, i);
                intervals.remove(i+1);
                //redo the processes once an interval is merged
                // [[0,3],[1,2],[1,5]] -> [[0,5]]
                i--;
			} 
		}
		return intervals;
	}
    
    public int getValidEnd(List<Interval> intervals, int i){
        return intervals.get(i).end < intervals.get(i + 1).end ? intervals.get(i + 1).end
								: intervals.get(i).end;
    }
}