Given an integer, return its base 7 string representation.

Example 1:

Input: 100Output: "202"

Example 2:

Input: -7Output: "-10"

Note: The input will be in range of [-1e7, 1e7].

class Solution(object):    def convertToBase7(self, num):        """        :type num: int        :rtype: str        """        """        Input: 100Output: "202"100%7=14,214%7=2,02%7=2,xxx        """        is_neg = False        if num < 0:                        num = -num            is_neg = True        ans = ""        while num >= 7:            ans = str(num%7) + ans            num = num/7        ans = str(num) + ans        return ans if not is_neg else "-"+ans

 

or

class Solution(object):    def convertToBase7(self, num):        """        :type num: int        :rtype: str        """        """        Input: 100Output: "202"100%7=14,214%7=2,02%7=2,xxx        """        if num == 0:            return '0'        is_neg = False        if num < 0:                        num = -num            is_neg = True                ans = ""        while num != 0:            ans = str(num%7) + ans            num = num/7                return ans if not is_neg else "-"+ans

使用递归：

class Solution(object):    def convertToBase7(self, num):        """        :type num: int        :rtype: str        """        if num < 0:            return "-"+self.convertToBase7(-num)        if num < 7:            return str(num)        return self.convertToBase7(num/7) + str(num%7)