205. Isomorphic Strings

Problem

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.

Solution

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isIsomorphic = function(s, t) {
    if (s.length !== t.length) return false;
    var map = {};
    var used = {};
    for (var i = 0; i < s.length; i++) {
        if (map[s[i]]) {
            if (map[s[i]] !== t[i]) return false;
        } else {
            if (used[t[i]]) return false;
            used[t[i]] = true;
            map[s[i]] = t[i];
        }
    }
    return true;
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).