Given two strings $5$ 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