For two strings to be isomorphic, all occurrences of a character in string A can be replaced with another character to get string B. The order of the characters must be preserved. There must be one-to-one mapping for ever char of string A to every char of string B.
paper
andtitle
would return true.egg
andsad
would return false.dgg
andadd
would return true.
isIsomorphic("egg", 'add'); // true
isIsomorphic("paper", 'title'); // true
isIsomorphic("kick", 'side'); // false
function isIsomorphic(firstString, secondString) {
// Check if the same lenght. If not, they cannot be isomorphic
if (firstString.length !== secondString.length) return false
var letterMap = {};
for (var i = 0; i < firstString.length; i++) {
var letterA = firstString[i],
letterB = secondString[i];
// If the letter does not exist, create a map and map it to the value
// of the second letter
if (letterMap[letterA] === undefined) {
letterMap[letterA] = letterB;
} else if (letterMap[letterA] !== letterB) {
// Eles if letterA already exists in the map, but it does not map to
// letterB, that means that A is mapping to more than one letter.
return false;
}
}
// If after iterating through and conditions are satisfied, return true.
// They are isomorphic
return true;
}