Isomorphic Strings

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

Problem Description

Given two strings s and t, determine if they are isomorphic.

Two strings 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.

For example, Given "egg", "add", return true.

Given "foo", "bar", return false.

Given "paper", "title", return true.

public boolean isIsomorphic(String s, String t) {
    if (s.length() != t.length()) return false;

    Map<Character, Character> map = new HashMap();

    for (int i = 0; i < s.length(); i++) {
        char c1 = s.charAt(i);
        char c2 = t.charAt(i);

        if ((!map.containsKey(c1)) {
            // since it is one to one mapping
            // we have to make sure that the key-value are both
            if (!map.containsValue(c2)) {
                map.put(c1, c2);
            } else {
                return false;
            }

        } else {
            if (map.get(c1) != c2)
                return false;
        }
    }

    return true;
}