Leetcode 205. Isomorphic Strings

QUESTION:

CODE SOLUTION:

class Solution(object):
    def isIsomorphic(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: bool
        """
        s_dict = {}
        t_dict = {}
        
        if len(s) != len(t):
            return False
        
        for i in range(len(s)):
            if s[i] not in s_dict:
                s_dict[s[i]] = t[i]
           
            if t[i] not in t_dict:
                t_dict[t[i]] = s[i]
            if s_dict[s[i]] != t[i] or t_dict[t[i]] != s[i]:
                return False
            
        return True
Time Complexity: O(N)
Space Compexity: O(1)

EXPLAINATION:

INPUT:

s = egg

t = add

So what happened?

We declared 2 dictionaries, s_dict and t_dict

If s and t have different word length, then it is not isomorphic

What happened inside the for loop (we used s length because we know s and t have same length). In this case, the loop will run 3 times because s length is 3.

1st iteration:

since both s_dict and t_dict are empty, after 1st iteration, we have: