README_EN.md

401. Binary Watch

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Description

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"]

Note:

• The order of output does not matter.
• The hour must not contain a leading zero, for example "01:00" is not valid, it should be "1:00".
• The minute must be consist of two digits and may contain a leading zero, for example "10:2" is not valid, it should be "10:02".

Solutions

Python3

class Solution:
    def readBinaryWatch(self, num: int) -> List[str]:
        return ['{:d}:{:02d}'.format(i, j) for i in range(12) for j in range(60) if (bin(i) + bin(j)).count('1') == num]

Java

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

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