Check two given strings are isomorphic in JavaScript
Last Updated : 03 Jul, 2024
Two strings are said to be isomorphic if it is possible to map every character of the first string to every character of the second string. Basically, in isomorphic strings, there is a one-to-one mapping between every character of the first string to every character of the second string. We can also explain this by saying that each character of the second string replaces each character of the first string.
Example 1:
str1 = 'ABCA'
str2 = 'XYZX'
'A' maps to 'X'
'B' maps to 'Y'
'C' maps to 'Z'
Here, mapping is possible between every character of the first string and every second string character. So str1 and str2 are isomorphic.
Example 2:
str1 = 'ABCA'
str2 = 'WXYZ'
'A' maps to 'W'
'B' maps to 'X'
'C' maps to 'Y'
'A' again maps to 'Z'
These two strings are not isomorphic because character 'A' from the first string is mapping with two characters from the second string.
We can check two given strings are isomorphic in Javascript in two ways:
Using Naive Approach
In this approach, we will compare each character of the first string with another character of the first string likewise for the second string. The current character of both strings shouldn't be equal to other characters. The time complexity of this approach is O(N^2) where n is the length of the string. This is a brute-force approach which is not very efficient.
This is the implementation of the above approach.
JavaScript function isStringIsomorphic(str1, str2) { if (str1.length !== str2.length) { return false; } for (let i = 0; i < str1.length; i++) { for (let j = i + 1; j < str1.length; j++) { if ( (str1[i] === str1[j] && str2[i] !== str2[j]) || (str1[i] !== str1[j] && str2[i] === str2[j]) ) { return false; } } } return true; } str1 = "ABCA"; str2 = "XYZX"; console.log(isStringIsomorphic(str1,str2)); By using hashmap
To check if strings are isomorphic or not, we have to take care of the following conditions:
- The length of both strings should be equal
- The current character of both strings shouldn't be mapped with other characters already.
We will use a hashmap to store the mapping between characters from str1 to those of str2. We will also use a Set to store the already mapped characters of str2.
Below is the implementation of the above approach.
JavaScript // JavaScript program for above approach // Function to check isomorphic strings function isIsomorphic(str1, str2) { // If length of strings are not equal then // they are not isomorphic if (str1.length !== str2.length) { return false; } // Map to store the mapping between // characters of first string to second const map = new Map(); // Set to store the already mapped // character of second string const set = new Set(); for (let i = 0; i < str1.length; i++) { // Taking ith char from both strings char1 = str1.charAt(i); char2 = str2.charAt(i); // If char1 has already been mapped if (map.has(char1) == true) { // Then we have to check that // mapped char should be same if (map.get(char1) !== char2) { return false; } } // If char1 is appearing for the first time else { // Check in the set that the char2 // is already there or not if (set.has(char2)) { return false; } // If none of above condition is true // it means both char1 and char2 are // appearing for the first time // insert them into the map map.set(char1, char2); set.add(char2); } } return true; } str1 = "ABCA"; str2 = "XYZX"; console.log(isIsomorphic(str1, str2)); Using Maps
Using two maps, one for each string, track character mappings. Iterate through both strings, checking if corresponding characters are mapped differently. If so, return false; otherwise, continue. If all mappings are consistent, return true.
Example: The function isStringIsomorphic checks if two strings str1 and str2 are isomorphic, i.e., if characters in str1 can be mapped uniquely to characters in str2, and vice versa.
JavaScript function isStringIsomorphic(str1, str2) { if (str1.length !== str2.length) { return false; } const map1 = new Map(); const map2 = new Map(); for (let i = 0; i < str1.length; i++) { const char1 = str1[i]; const char2 = str2[i]; if (map1.has(char1)) { if (map1.get(char1) !== char2) { return false; } } else { map1.set(char1, char2); } if (map2.has(char2)) { if (map2.get(char2) !== char1) { return false; } } else { map2.set(char2, char1); } } return true; } const str1 = "ABCA"; const str2 = "XYZX"; console.log(isStringIsomorphic(str1, str2)); Using String Replacement and Comparison
Using string replacement and comparison to check if two strings are isomorphic involves mapping each character in both strings to a new unique character sequence. If the transformed sequences are identical, the strings are isomorphic.
Example
JavaScript const areIsomorphic = (s, t) => { const replaceChars = (str) => { const map = {}; let newStr = ''; let charCode = 0; for (let char of str) { if (!map[char]) { map[char] = String.fromCharCode(charCode++); } newStr += map[char]; } return newStr; }; return replaceChars(s) === replaceChars(t); }; console.log(areIsomorphic("egg", "add")); // true console.log(areIsomorphic("foo", "bar")); // false