public class Solution {
    public List<String> readBinaryWatch(int num) {
        List<String> times = new ArrayList<String>();
        for(int h=0; h<12; h++) {
            for(int m=0; m<60; m++) {
                if(Integer.bitCount(h) + Integer.bitCount(m) == num) {
                    times.add(String.format("%d:%02d", h, m));
                }
            }
        }
        return times;
    }
}