Isomorphic Strings

1-isomorphic.js

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isIsomorphic = function(s, t) {
    var result = true;

    if (s.length === t.length) {
        var hash1 = [];
        var hash2 = [];

        for (var i=0; i<s.length; i++) {
            var char1 = s[i];
            var char2 = t[i];
        
            // If the character's last seen position doesn't match up, then not isomorphic.
            if (hash1[char1] !== hash2[char2]) {
                result = false;
                break;
            }
            else {
                // Store the last seen position of this character.
                hash1[char1] = i;
                hash2[char2] = i;
            }
        }
    }
    else {
        result = false;
    }

    return result;
};

2-isomorphic.js

//
// This works, but is slower.
//

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isIsomorphic = function(s, t) {
    var result = false;
    
    if (s.length === t.length) {
        for (var i=0; i<s.length; i++) {
            var char1 = s[i];
            var char2 = t[i];
            
            var re1 = new RegExp(char1, "g");
            var re2 = new RegExp(char2, "g");
            s = s.replace(re1, i);
            t = t.replace(re2, i);
        }

        result = s === t;
    }
    
    return result;
};

isomorphic.js

/*
https://js-algorithms.tutorialhorizon.com/2015/10/21/determine-if-given-strings-are-isomorphic/
*/
function isomorphic (str1, str2) {
	
    var len1 = str1.length;
    
    if (len1 != str2.length) {
        console.log('Both strings have different lenghts');
    	return false;
    }
    
    var chMap = {};
    
    for (var i = 0; i < len1; i++) {
    	
        if (!chMap[str1[i]]) {   	
            chMap[str1[i]] = str2[i];
     
        } else if (chMap[str1[i]] !== str2[i]) {
        	console.log('Both strings differ in maaping at index ' + i);
            return false;
        }
    }
    return true;
}

zexample.txt

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.

Note:
You may assume both s and t have the same length.