Given an integer, return its base 7 string representation.

Example 1:

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Input: 100
Output: "202"

Example 2:

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Input: -7
Output: "-10"

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

思路

简单的7进制转换，采用短除法即可实现。

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class Solution(object):
    def convertToBase7(self, num):
        """
        :type num: int
        :rtype: str
        """
        
        isNeg = False
        if (num < 0):
            num = -num
            isNeg = True
        elif (num == 0):
            return "0"
        res = ""
        while (num):
            tmp = num % 7
            res = str(tmp) + res
            num = num / 7
        if (isNeg):
            return "-" + res
        else:
            return res