LeetCode#205 Isomorphic Strings

Problem Definition:

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.

For example,
Given "egg", "add", return true.

Given "foo", "bar", return false.

Given "paper", "title", return true.

Note:
You may assume both s and t have the same length.

Solution: 利用字典 dict, 一次遍历，双向映射

def isIsomorphic(s, t):
        d1,d2={},{}
        for a,b in zip(s,t):
            if a not in d1:
                d1[a]=b
            else:
                if d1[a]!=b:
                    return False
            if b not in d2:
                d2[b]=a
            else:
                if d2[b]!=a:
                    return False
        return True