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 * 10^4
• t.length == s.length
• s and t consist of any valid ascii character.

Code

C++

class Solution
{
public:
    bool isIsomorphic(string s, string t)
    {
        map<char, char> m; // map
        map<char, bool> v; // visit

        for (int i = 0; i < s.length(); i++)
        {
            if (!m[s[i]])
            {
                m[s[i]] = t[i]; // s[i]'s pair is t[i]
                if (v[t[i]] != true)
                    v[t[i]] = true; // 1:1 pair
                else
                    return false;
            }
            else
            { 
                if (m[s[i]] != t[i])
                    return false;
            }
        }
        return true;
    }
};