205. Isomorphic Strings

java/205-Isomorphic-Strings.java

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+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

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+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
+ }
+}