Question

How to check if two strings are isomorphic in TypeScript

Answer 1

// Two strings are isomorphic if characters in one can be replaced to get the other, 
// while preserving the order.

function areIsomorphic(s: string, t: string): boolean {
    if (s.length !== t.length) return false;

    const mapST: Map<string, string> = new Map<string, string>();
    const mapTS: Map<string, string> = new Map<string, string>();

    for (let i = 0; i < s.length; i++) {
        const c1: string = s[i];
        const c2: string = t[i];

        // Check mapping from s → t
        if (mapST.has(c1)) {
            if (mapST.get(c1) !== c2) return false;
        } else {
            mapST.set(c1, c2);
        }

        // Check mapping from t → s
        if (mapTS.has(c2)) {
            if (mapTS.get(c2) !== c1) return false;
        } else {
            mapTS.set(c2, c1);
        }
    }

    return true;
}

console.log(areIsomorphic("egg", "add"));     
console.log(areIsomorphic("foo", "bar"));     
console.log(areIsomorphic("paper", "title")); 



/*
run:

true
false
true

*/

 

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Answer 2

function areIsomorphic(s: string, t: string): boolean {
    const pattern: (str: string) => number[] = (str: string) => [...str].map(ch => str.indexOf(ch));
    
    return pattern(s).join() === pattern(t).join();
}

console.log(areIsomorphic("egg", "add"));     
console.log(areIsomorphic("foo", "bar"));     
console.log(areIsomorphic("paper", "title")); 



/*
run:

true
false
true

*/

 

70+ SQL courses for beginners and professionals