# LeetCode 246. Strobogrammatic Number

## 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

Create a reference mapping for strobo grammatic numbers. Then use the two-pointer technique to check if the numbers from left and right match the mapping.

## Python Solution

``````class Solution:
def isStrobogrammatic(self, num: str) -> bool:
mapping = {"9": "6", "6": "9", "8": "8", "1": "1", "0": "0"}

left = 0
right = len(num) - 1

while left <= right:
if num[left] in mapping and mapping[num[left]] == num[right]:
left += 1
right -= 1
else:
return False

return True
``````
• Time Complexity: ~N
• Space Complexity: ~1