0205. Isomorphic Strings

https://leetcode.com/problems/isomorphic-strings

Description

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.

ac

class Solution {
    public boolean isIsomorphic(String s, String t) {
        // edge cases
        if (s.length() != t.length()) return false;

        Map<Character, Character> map = new HashMap<>();
        Set<Character> set = new HashSet<>();
        for (int i = 0; i < s.length(); i++) {
            char cs = s.charAt(i);
            char ct = t.charAt(i);
            if (!map.containsKey(cs)) {
                if (set.contains(ct)) return false;
                map.put(cs, ct);
                set.add(ct);
            } else {
                if (map.get(cs) != ct) return false;
            }
        }

        return true;
    }
}