Strobogrammatic Number - Python Leetcode

 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: num = "69"
Output: true

Example 2:

Input: num = "88"
Output: true

Example 3:

Input: num = "962"
Output: false

Example 4:

Input: num = "1"
Output: true

TC: O(N) SC:O(1)

Solution 1:

class Solution:
    def isStrobogrammatic(self, num: str) -> bool:
        if not num:
            return True
        map = {'0':'0','1':'1','6':'9','8':'8','9':'6','2':'','3':'','4':'','5':'','7':''}
        i = 0
        j = len(num)-1
        while i<=j:
            if num[i] != map[num[j]]:
                return False
            i+=1
            j-=1
        return True

Solution 2:

class Solution:
    def isStrobogrammatic(self, num: str) -> bool:
        if not num:
            return True
        map = {'0':'0','1':'1','6':'9','8':'8','9':'6'}
        i = 0
        j = len(num)-1
        while i<=j:
            if num[j] not in map or num[i] != map[num[j]]:
                return False
            i+=1
            j-=1
        return True