public class Solution {
public List<String> readBinaryWatch(int num) {
List<String> rst = new ArrayList<String>();
int[] nums1 = new int[]{8, 4, 2, 1};
int[] nums2 = new int[]{32, 16, 8, 4, 2, 1};
for (int i = 0; i <= num; i++) {
for (Integer h : getSumList(nums1, i)) {
if (h > 11) continue;
for (Integer m : getSumList(nums2, num - i)) {
if (m > 59) continue;
String time = h + ":" + (m > 9 ? m : "0" + m);
rst.add(time);
}
}
}
return rst;
}
private List<Integer> getSumList(int[] nums, int count) {
List<Integer> list = new ArrayList<>();
getSumListHelper(nums, count, 0, 0, list);
return list;
}
private void getSumListHelper(int[] nums, int count, int pos, int sum, List<Integer> list) {
if (count == 0) {
list.add(sum);
return;
}
for (int i = pos; i < nums.length; i++) {
getSumListHelper(nums, count - 1, i + 1, sum + nums[i], list);
}
}
}