78. Subsets

样例
输入
{1,8,5,4}

输出

[[], [1], [1, 4], [1, 4, 5], [1, 4, 5, 8], [1, 4, 8], [1, 5], [1, 5, 8], [1, 8], [4], [4, 5], [4, 5, 8], [4, 8], [5], [5, 8], [8]]

public List<List<Integer>> allSubList(int[] arr){
    List<Integer> temp = new ArrayList<>();
    List<List<Integer>> result = new ArrayList<>();
    Arrays.sort(arr);
    group(arr, temp, result, 0);
    return result;
}

private void group(int[] arr, List<Integer> temp, List<List<Integer>> result, int index){
    result.add(new ArrayList<>(temp));
    if (temp.size() == arr.length)
        return;
    for(int i = index; i < arr.length; i++){
        temp.add(arr[i]);
        group(arr, temp, result,i+1);
        temp.remove(temp.size()-1);
    }
}