MergeIntervals.java

import java.util.Arrays;
import java.util.LinkedList;

/**
 * Leetcode problem #56, Merge Intervals
 * https://leetcode.com/problems/merge-intervals/description/
 */
public class MergeIntervals {
    public static void main(String[] args) {
        int[][] intervals = { { 1, 3 }, { 2, 6 }, { 8, 10 }, { 15, 18 } };
        int[][] mergedIntervals = merge(intervals);
        System.out.println(Arrays.deepToString(mergedIntervals));
    }

    public static int[][] merge(int[][] intervals) {
        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
        LinkedList<int[]> list = new LinkedList<>();
        int[] current = intervals[0];
        for (int i = 1; i < intervals.length; i++) {
            if (current[1] >= intervals[i][0]) {
                current[1] = Math.max(current[1], intervals[i][1]);
            } else {
                list.add(current);
                current = intervals[i];
            }
        }
        list.add(current);
        return list.toArray(new int[list.size()][]);
    }
}