Isomorphic Strings: Accepted

gouthampradhan · gouthampradhan · commit 2b187efda395 · 2018-04-12T00:00:40.000+02:00
diff --git a/README.md b/README.md
@@ -257,6 +257,7 @@ My accepted leetcode solutions to some of the common interview problems.
 - [Count and Say](problems/src/string/CountAndSay.java) (Easy)
 - [Multiply Strings](problems/src/string/MultiplyStrings.java) (Medium)
 - [Longest Word in Dictionary through Deleting](problems/src/string/LongestWordInDictonary.java) (Medium)
+- [Isomorphic Strings](problems/src/string/IsomorphicStrings.java) (Easy)
 
 #### [Tree](problems/src/tree)
 
diff --git a/problems/src/string/IsomorphicStrings.java b/problems/src/string/IsomorphicStrings.java
@@ -0,0 +1,54 @@
+package string;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Created by gouthamvidyapradhan on 11/04/2018.
+ * Given two strings s and t, determine if they are isomorphic.
+
+ Two strings are isomorphic if the characters in s can be replaced to get t.
+
+ All occurrences of a character must be replaced with another character while preserving the order of characters. No
+ two characters may map to the same character but a character may map to itself.
+
+ For example,
+ Given "egg", "add", return true.
+
+ Given "foo", "bar", return false.
+
+ Given "paper", "title", return true.
+
+ Note:
+ You may assume both s and t have the same length.
+ Solution O(N): Maintain two hashmaps and compare character by character.
+ */
+public class IsomorphicStrings {
+    /**
+     * Main method
+     * @param args
+     * @throws Exception
+     */
+    public static void main(String[] args) throws Exception{
+        System.out.println(new IsomorphicStrings().isIsomorphic("abc", "dea"));
+    }
+
+    public boolean isIsomorphic(String s, String t) {
+        if(s.length() != t.length()) return false;
+        Map<Character, Character> first = new HashMap<>();
+        Map<Character, Character> second = new HashMap<>();
+        for(int i = 0; i < s.length(); i ++){
+            char c = s.charAt(i);
+            if(first.containsKey(c)){
+                char secondC = first.get(c);
+                if(t.charAt(i) != secondC) return false;
+            } else{
+                first.put(c, t.charAt(i));
+                if(second.containsKey(t.charAt(i))) return false;
+                second.put(t.charAt(i), c);
+            }
+        }
+        return true;
+    }
+
+}
