246. Strobogrammatic-Number.md

Description

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).

Write a function to determine if a number is strobogrammatic. The number is represented as a string.

Example 1:

Input:  "69"
Output: true

Example 2:

Input:  "88"
Output: true

Example 3:

Input:  "962"
Output: false

---

Solution

• 根据题目要求，num中所有数字必须为0、1、6、8、9，才有可能是一个strobogrammatic number。
• 这几个数字对应0, 1, 9, 8, 6, 倒序遍历num，看组成的数字是否与原num相等即可。

class Solution:
    def isStrobogrammatic(self, num):
        """
        :type num: str
        :rtype: bool
        """
        d = {"0": "0", "1": "1", "6": "9", "8": "8", "9": "6"}
        strobogrammatic = ""
        for i in num[::-1]:
            if i in d:
                strobogrammatic += d[i]
            else:
                return False
        return strobogrammatic == num