56. Merge Intervals

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Problem

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 considered overlapping.

Code

class Solution {
    public int[][] merge(int[][] intervals) {
        if(intervals == null || intervals.length == 0) return intervals;
        List<int[]> res = new ArrayList<>();

        Arrays.sort(intervals, (a, b) ->(a[0] - b[0]));

        int[] curr = intervals[0];

        for(int i = 1; i < intervals.length; i++){
            if(intervals[i][0] > curr[1]){
                res.add(curr);
                curr = intervals[i];
            } else {
                curr[1] = Math.max(curr[1], intervals[i][1]);
            }
        }

        res.add(curr);

        return res.toArray(new int[res.size()][2]);
    }
}