A binary watch has 4 LEDs on the top which represent the hours (0-11), and the 6 LEDs on the bottom represent the minutes (0-59).
Each LED represents a zero or one, with the least significant bit on the right.
For example, the above binary watch reads "3:25".
Given a non-negative integer n which represents the number of LEDs that are currently on, return all possible times the watch could represent.
Example:
Input: n = 1 Return: ["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
public class Solution { public List<String> readBinaryWatch(int num) { List<String> s=new ArrayList<>(); for(int h=0;h<12;h++) { for(int m=0;m<60;m++) { if(Integer.bitCount(h*64+m)==num) { s.add(String.format("%d:d",h,m)); } } } return s; } }