Hashing-1 isIsomorphic Hw

GroupAnagrams.java

@@ -0,0 +1,29 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+
+public class GroupAnagrams {
+    public List<List<String>> groupAnagrams(String[] strs){
+        HashMap<String, List<String>> map = new HashMap<>();
+        for(int i=0;i<strs.length;i++){
+            String curr=strs[i];
+            //sorting character array and get String back
+            char [] charArr = curr.toCharArray(); ////Breaks the string "eat" into individual characters and stores in charArr -- ['e', 'a', 't']
+            Arrays.sort(charArr); //'e', 'a', 't'} → {'a', 'e', 't'}
+            String sorted = String.valueOf(charArr); //converts character array to string "aet"
+            //if map contains sorted, if not then add sorted string initiate with a new arraylist
+            if(!map.containsKey(sorted)){
+                map.put(sorted, new ArrayList<>()); //map = {"aet" : []} creates new empty list
+            }
+            //get list of all Strings
+            List<String> li = map.get(sorted);
+            li.add(curr); //add to list
+            map.put(sorted,li);//add to map
+        }
+        return new ArrayList<>(map.values());
+    }
+}
+
+//TC: O(N KlogK)
+//SC: O(NK)

IsIsomorphic.java

@@ -0,0 +1,42 @@
+import java.util.HashMap;
+
+public class IsIsomorphic {
+    public static void main(String args[]){
+        String s = "paper";
+        String t = "title";
+        System.out.println(isIsomorphic(s,t));
+    }
+    public static boolean isIsomorphic(String s, String t) {
+        int sl = s.length();
+        int tl = t.length();
+        //create two HashMaps to store characters of s & t
+        HashMap<Character, Character> sMap = new HashMap<>();
+        HashMap<Character, Character> tMap = new HashMap<>();
+        for(int i=0; i < sl; i++){
+            char sChar = s.charAt(i);
+            char tChar = t.charAt(i);
+            //s to t mapping
+            if(sMap.containsKey(sChar)){
+                //if earlier mapped character of s is equal to t, if not return false --> breech
+                if(sMap.get(sChar) != tChar){
+                    return false;
+                }
+            } else{
+                sMap.put(sChar, tChar);
+            }
+            // t to s mapping
+            if(tMap.containsKey(tChar)){
+                //if earlier mapped character of t is equal to s, if not return false --> breech
+                if(tMap.get(tChar) != sChar){
+                    return false;
+                }
+            } else{
+                tMap.put(tChar, sChar);
+            }
+        }
+        return true;
+    }
+}
+
+// TC : O(N)
+//SC : O(1)