56. Merge Intervals

Given a collection of intervals, merge all overlapping intervals.

Example 1:

Input: [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6].

Example 2:

Input: [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] are considerred overlapping.

public List<Interval> merge(List<Interval> intervals) {
        if (intervals.size() <= 1) return intervals;
        List<Interval> result = new ArrayList<>();
        Collections.sort(intervals, Comparator.comparingInt(o -> o.start));
        for (int i = 1; i < intervals.size(); i++) {
            Interval left = intervals.get(i-1);
            Interval right = intervals.get(i);
            if (left.end < right.start) {
                result.add(left);
            } else {
                right.start = left.start;
                right.end = Math.max(left.end, right.end);
            }
            if (i == intervals.size()-1) result.add(right);
        }
        return result;
}