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public int[][] merge(int[][] intervals) {
    if (intervals.length <= 1) return intervals;
    
    Arrays.sort(intervals, new Comparator<int[]>(){
        public int compare(int[] a, int[] b) {
            return a[0] - b[0];
        }
    });
    List<int[]> res = new ArrayList<>();
    res.add(intervals[0]);
    
    for (int[] i : intervals) {
        if (res.get(res.size() - 1)[1] < i[0]) res.add(i);
        else {
            res.get(res.size() - 1)[1] = Math.max(res.get(res.size()-1)[1], i[1]);
        }
    }
    
    return res.toArray(new int[res.size()][2]);
}
  • ArrayList to Array: someArrayList.toArray()
  • Object[] toArray(): 直接调用返回的是Object[]类型的array, 一般都不这样用
  • <T> T[] toArray(T[] a): a: the array into which all elements of list are to be stored, if it is big enough; otherwise, a new arrya of the same type is allocated for this purpose.