Question

How to check if two strings are isomorphic in Swift

Answer 1

import Foundation

func areIsomorphic(_ s: String, _ t: String) -> Bool {
    guard s.count == t.count else { return false }

    var mapST: [Character: Character] = [:]
    var mapTS: [Character: Character] = [:]

    for (c1, c2) in zip(s, t) {
        // Check mapping from s → t
        if let mapped = mapST[c1] {
            if mapped != c2 { return false }
        } else {
            mapST[c1] = c2
        }

        // Check mapping from t → s
        if let mapped = mapTS[c2] {
            if mapped != c1 { return false }
        } else {
            mapTS[c2] = c1
        }
    }
    return true
}

print(areIsomorphic("egg", "add"))     
print(areIsomorphic("foo", "bar"))     
print(areIsomorphic("paper", "title")) 



/*
run:

true
false
true

*/

 

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Answer 2

import Foundation

func areIsomorphic(_ s: String, _ t: String) -> Bool {
    func pattern(_ str: String) -> [Int] {
        return str.enumerated().map { idx, ch in str.firstIndex(of: ch)!.utf16Offset(in: str) }
    }
    
    return pattern(s) == pattern(t)
}

print(areIsomorphic("egg", "add"))     
print(areIsomorphic("foo", "bar"))     
print(areIsomorphic("paper", "title")) 



/*
run:

true
false
true

*/

 

70+ SQL courses for beginners and professionals