205

205. Isomorphic Strings (Easy)

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.

Companies:
Amazon, Uber

Related Topics:
Hash Table, String

Similar Questions:

• Word Pattern (Easy)

Solution 1.

// OJ: https://leetcode.com/problems/isomorphic-strings/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(1)
class Solution {
public:
    bool isIsomorphic(string s, string t) {
        unordered_map<char, char> m, r;
        for (int i = 0; i < s.size(); ++i) {
            if (m.count(s[i]) && m[s[i]] != t[i]) return false;
            if (r.count(t[i]) && r[t[i]] != s[i]) return false;
            m[s[i]] = t[i];
            r[t[i]] = s[i];
        }
        return true;
    }
};