# 205.isomorphic-strings

## Statement

• Difficulty: Easy
• Tag: `哈希表` `字符串`

``````输入：s = "egg", t = "add"

``````

``````输入：s = "foo", t = "bar"

``````输入：s = "paper", t = "title"

• `1 <= s.length <= 5 * 104`
• `t.length == s.length`
• `s` 和 `t` 由任意有效的 ASCII 字符组成

• Difficulty: Easy
• Tag: `Hash Table` `String`

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.

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
``````

Constraints:

• `1 <= s.length <= 5 * 104`
• `t.length == s.length`
• `s` and `t` consist of any valid ascii character.

## Solution

``````class Solution:
def isIsomorphic(self, s: str, t: str) -> bool:
sd = {}
st = {}
for i in range(len(s)):
try:
if sd[s[i]] != t[i]:
return False
except KeyError:
sd[s[i]] = t[i]

try:
if st[t[i]] != s[i]:
return False
except KeyError:
st[t[i]] = s[i]

return True
``````