#56合并区间

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

final class Solution {
    public int[][] merge(int[][] intervals) {
        if (intervals.length == 0) return new int[0][2];
        Arrays.sort(intervals, (first, second) -> Integer.compare(first[0], second[0]));
        List<int[]> merged = new ArrayList<>();
        int left = intervals[0][0];
        int right = intervals[0][1];
        for (int i = 1; i < intervals.length; i++) {
            if (intervals[i][0] > right) {
                merged.add(new int[] {left, right});
                left = intervals[i][0];
                right = intervals[i][1];
            } else {
                right = Math.max(right, intervals[i][1]);
            }
        }
        merged.add(new int[] {left, right});
        return merged.toArray(int[][]::new);
    }
}