Check whether the strings are isomorphic.
Example 1
Input: s = "egg", t = "add"
Output: True
Explanation: e->a and g->d form a one-to-one mapping.
Output: True
Explanation: e->a and g->d form a one-to-one mapping.
Example 2
Input: s = "foo", t = "bar"
Output: False
Explanation: The character o in the first string would have to map to both a and r, which is impossible.
Output: False
Explanation: The character o in the first string would have to map to both a and r, which is impossible.