205. Isomorphic Strings

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.

class Solution {
public:
    bool isIsomorphic(string s, string t)
    {
        unordered_map<char, int> m1;
        unordered_map<char, int> m2;

        int n = t.size();

        for (int i = 0; i < n; i++)
        {
            if (m1[s[i]] != m2[t[i]])
            {
                return false;
            }
            m1[s[i]] = i + 1;
            m2[t[i]] = i + 1;
        }
        return true;
    }
};

• T: $O(N)$
• S: $O(N)$