205. isomorphic string

205. Isomorphic Strings

Original title link ：https://leetcode.cn/problems/isomorphic-strings/

Given two strings s and t , Judge whether they are isomorphic .

If s The characters in can be replaced according to some mapping relationship t , So these two strings are isomorphic .

Every character that appears should be mapped to another character , Without changing the order of characters . Different characters cannot be mapped to the same character , The same character can only be mapped to the same character , Characters can be mapped to themselves .

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

Tips ：

1 <= s.length <= 5 * 104
t.length == s.length
s and t By any valid ASCII Character composition

Their thinking ：

Use two hash tables ,key Is the character of the current string ,value Is the character of the opposite string .

Code implementation ：

class Solution:
    def isIsomorphic(self, s: str, t: str) -> bool:
        d1, d2 = {
    }, {
    }

        for i in range(len(s)):
            if ((s[i] in d1 and d1[s[i]] != t[i]) or (t[i] in d2 and d2[t[i]] != s[i])):
                return False
            
            d1[s[i]] = t[i]
            d2[t[i]] = s[i]

        return True