205. Isomorphic Strings

Solution idea

Use two HashMaps:

map dict: map each char in s to the char of the same position in t. map dict is to check that if there is a repeated char in s, it must be mapped to the same char that was previously mapped to in t.

map checkDups: a set that contains all chars in t that have been scanned. map checkDups is to ensure "No two characters may map to the same character".

Time complexity = $O(n)$

Exactly same idea as 290. Word Pattern