Leetcode 0246: Strobogrammatic Number

Leetcode 0246: Strobogrammatic Number"/>

Leetcode 0246: Strobogrammatic Number

题目描述：

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

Time complexity: O(n)
Space complexity : O(1)

class Solution {public boolean isStrobogrammatic(String num) {Map<Character, Character> map = new HashMap<> (Map.of('0', '0', '1', '1', '6', '9', '8', '8', '9', '6'));for(int l = 0, r = num.length()-1; l <= r; l++,r--){char lc = num.charAt(l);char rc = num.charAt(r);if(!map.containsKey(lc) || map.get(lc) != rc){return false;}}return true;}
}