56. Merge Intervals

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].

代码如下：

/**
 * 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 {
    @SuppressWarnings("unchecked")
    public static List<Interval> partMerge(List<Interval> intervals){
        intervals.sort(new Comparator(){
            @Override
            public int compare(Object o1, Object o2) {
                Interval i1 = (Interval)o1;
                Interval i2 = (Interval)o2;
                if(i1.start!=i2.start)
                    return i1.start-i2.start;
                else
                    return (Math.abs(i1.end-i1.start)-Math.abs(i2.end-i2.start));
            }
        });
        
        List<Integer> removeList = new ArrayList<Integer>();
        for(int i = 0;i < intervals.size()-1; i++ )
            if(intervals.get(i).end>=intervals.get(i+1).start&&intervals.get(i).end<=intervals.get(i+1).end){
                    intervals.get(i+1).start = intervals.get(i).start;
                    removeList.add(i);
            }else if(intervals.get(i).end>=intervals.get(i+1).end){
                intervals.get(i+1).end = intervals.get(i).end;
                intervals.get(i+1).start = intervals.get(i).start;
                removeList.add(i);
            }
        for(int i = removeList.size()-1; i>=0 ; i--){
            intervals.remove(intervals.get(removeList.get(i)));
        }
        return intervals;
    }
    public List<Interval> merge(List<Interval> intervals) {
        int presize = 0;
        do{
            presize = intervals.size();
            intervals = partMerge(intervals);
        }while(presize!=intervals.size());
        return intervals;
    }
}