[LeetCode 056] Merge Intervals

Merge Intervals

Implementation

/**
 * 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 MyComparator implements Comparator<Interval> {
    public int compare(Interval in1, Interval in2) {
       return in1.start - in2.start;
    }
}

public class Solution {
    public List<Interval> merge(List<Interval> intervals) {
        Collections.sort(intervals, new MyComparator());
        List<Interval> result = new ArrayList<Interval>();
        Interval pre = null;
        for (Interval interval: intervals) {
            if (pre == null || pre.end < interval.start) {
                result.add(interval);
                pre = interval;
            }
            else {
                if (interval.end > pre.end) {
                    pre.end = interval.end;
                }
            }
        }
        return result;
    }
}

public class Solution {
    public List<Interval> merge(List<Interval> intervals) {
        Collections.sort(intervals, new MyComparator());
        List<Interval> result = new ArrayList<Interval>();
        for (int i = 0; i < intervals.size(); i++) {
            if (result.isEmpty()) {
                result.add(intervals.get(i));
            }
            else {
                Interval pre = result.get(result.size() - 1);
                Interval current = intervals.get(i);
                if (pre.end < current.start) {
                    result.add(current);
                }
                else if (pre.end <= current.end) {
                    pre.end = current.end;
                }
            }
        }
        return result;
    }
}