205. Isomorphic Strings

java/205-Isomorphic-Strings.java

@@ -0,0 +1,29 @@
+class Solution {
+    public boolean isIsomorphic(String s, String t) {
+        // Needs bidirectional mapping from s <--> t
+        if(s.length() != t.length()) {
+            return false;
+        }
+
+        Map<Character, Character> mapSourceToDest = new HashMap<>();
+        Map<Character, Character> mapDestToSource = new HashMap<>();
+
+        int len = s.length();
+        for(int i=0; i<len; i++) {
+            char sourceChar = s.charAt(i), destChar = t.charAt(i);
+            char sourceReturn = mapSourceToDest.getOrDefault(sourceChar, destChar);
+            if(sourceReturn != destChar) {
+                return false;
+            }
+            mapSourceToDest.put(sourceChar, destChar);
+
+            char destReturn = mapDestToSource.getOrDefault(destChar, sourceChar);
+            if(destReturn != sourceChar) {
+                return false;
+            }
+            mapDestToSource.put(destChar, sourceChar);
+        }
+
+        return true;
+    }
+}

swift/205-Isomorphic-Strings.swift

@@ -0,0 +1,24 @@
+class Solution {
+    func isIsomorphic(_ s: String, _ t: String) -> Bool {
+        guard s.count == t.count else { return false }
+
+        var mapSourceToDest: [Character: Character] = [:]
+        var mapDestToSource: [Character: Character] = [:]
+
+        for (sourceChar, destChar) in zip(s, t) {
+            if let sourceMapped = mapSourceToDest[sourceChar] {
+                guard sourceMapped == destChar else { return false }
+            } else {
+                mapSourceToDest[sourceChar] = destChar
+            }
+
+            if let destMapped = mapDestToSource[destChar] {
+                guard destMapped == sourceChar else { return false }
+            } else {
+                mapDestToSource[destChar] = sourceChar
+            }
+        }
+
+        return true
+    }
+}