401. Binary Watch

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Share 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”.

思路：大神StefanPochmann [‘%d:%02d’%(h,m) for h in range(12) for m in range(60) if (bin(h)+bin(m)).count(‘1’)==num] bin(h)+bin(m)为字符串，前缀0b不影响统计1的个数

代码：python3

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