[leetcode][401]. Binary Watch

下课了，做道简单题。

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".

import itertools

class Solution(object):
def getHour(self, n):
'''
n >=0 n<4
'''
if n==0:
return [0]
hours = []
idxs = [0,1,2,3]
temp = ['0','0','0','0']
for change_idxs in itertools.combinations(idxs,n):
for v in change_idxs:
temp[v] = '1'

value = int(''.join(temp),2)
for v in change_idxs:
temp[v] = '0'

if value <= 11:
hours.append(value)
return hours

def getMinutes(self, n):
'''
n>=0 n<=59
'''
if n==0:
return [0]
minutes = []
idxs = [0,1,2,3,4,5]
temp = ['0','0','0','0','0','0']
for change_idxs in itertools.combinations(idxs,n):
for v in change_idxs:
temp[v] = '1'
value = int(''.join(temp),2)
for v in change_idxs:
temp[v] = '0'
if value <= 59:
minutes.append(value)
return minutes

def readBinaryWatch(self, num):
"""
:type num: int
:rtype: List[str]
"""
ans = []
for h in range(4):
m = num-h
if m>=0:
hours = self.getHour(h)
minutes = self.getMinutes(m)
for h_val, m_val in itertools.product(hours,minutes):
ans.append('{}:{:0>2d}'.format(h_val,m_val))
return ans