504. Base 7

Given an integer, return its base 7 string representation.

Example 1:

Input: 100
Output: "202"

Example 2:

Input: -7
Output: "-10"

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

class Solution(object):
    def convertToBase7(self, num):
        """
        :type num: int
        :rtype: str
        """
        n = []
        flag = False
        if num<0:
            flag = True
            num = -num
        while True:
            n.append(str(num%7))
            num = int(num/7)
            if num ==0 :
                break
        if flag:
            return '-' + ''.join(n[::-1])
        return ''.join(n[::-1])

注意负号就可以