题目
Given two strings s and t, determine if they are isomorphic.
Two strings s and t 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.
解题思路
使用一个字典，存字母之间的映射，使用一个集合维护在第二个字符串中所有出现过的字母，如果映射冲突，或者不同字母映射到的字母在集合中出现，则不是同构
代码
class Solution:
def isIsomorphic(self, s: str, t: str) -> bool:
chars = set()
permutation = {}
for i in range(0, len(s)):
if s[i] not in permutation:
if t[i] in chars:
return False
else:
permutation[s[i]] = t[i]
chars.add(t[i])
else:
if t[i] != permutation[s[i]]:
return False
return True
