## Description

https://leetcode.com/problems/strobogrammatic-number/

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

## Explanation

## Python Solution

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

- Time Complexity: ~N
- Space Complexity: ~1