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 """ ans="" if num<0: neg=True else: neg=False num=abs(num) while num>=7: ans+=str(num%7) num=num//7 ans+=str(num) if neg: ans='-'+ans[::-1] return ans return ans[::-1]