[LeetCode 56] Merge Intervals

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * 
		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].
 *
 */

public class MergeIntervals {

	static class Interval {
		int start;
		int end;

		Interval() {
			start = 0;
			end = 0;
		}

		Interval(int s, int e) {
			start = s;
			end = e;
		}
	}
	
	
//	168 / 168 test cases passed.
//	Status: Accepted
//	Runtime: 326 ms
//	Submitted: 1 minute ago

    static List<Interval> merge(List<Interval> intervals) {
    	List<Interval> mergeIntervals = new ArrayList<Interval>();
		if(intervals.size() == 0) 
			return mergeIntervals;
		Collections.sort(intervals, new Comparator<Interval>() {
			public int compare(Interval int1, Interval int2) {
				return int1.start - int2.start;
				}
		});
		
		Interval preInterval = intervals.remove(0);
		for (Interval interval : intervals) {
			if (preInterval.end < interval.start) {
				mergeIntervals.add(preInterval);
				preInterval = interval;
			} else {
				if(preInterval.end < interval.end)
					preInterval.end = interval.end;
			}
		}
		mergeIntervals.add(preInterval);		
		return mergeIntervals;
	}
    
	public static void main(String[] args) {
    	Interval i1 = new Interval(2, 6);
    	Interval i2 = new Interval(1, 3);
    	Interval i3 = new Interval(8, 10);
    	Interval i4 = new Interval(15, 18);
		
		List<Interval> intervals = new ArrayList<Interval>();
		
		intervals.add(i1);
		intervals.add(i2);
		intervals.add(i3);
		intervals.add(i4);
		merge(intervals);
	}

}