Isomorphic Strings - Python Leetcode Solution

 Given two strings s and t, determine if they are isomorphic.

Two strings are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.

Example 1:

Input: s = "egg", t = "add"
Output: true

Example 2:

Input: s = "foo", t = "bar"
Output: false

Example 3:

Input: s = "paper", t = "title"
Output: true

class Solution:
    def isIsomorphic(self, s: str, t: str) -> bool:
        if s==t or (s is None and t is None):
            return True
        if len(s) != len(t):
            return False
        map = {}
        for i in range(len(s)):
            if s[i] not in map and t[i] not in map.values(): 
                map[s[i]] = t[i] 
            if s[i] not in map or map[s[i]] != t[i]:  
                return False
            
        return True