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.