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.

• Two strings s and t.

Input: s = "egg", t = "add"
Output: True Input: s = "foo", t = "bar"
Output: False