Completed Hashing-1

Problem1.java

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+// Time Complexity :isIsomorphic: O(2n)=O(n) , n is  number of characters in the string
+// Space Complexity :0(1)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this : nothing
+
+import java.util.HashMap;
+import java.util.HashSet;
+
+public class Problem1 {
+    public boolean isIsomorphic(String s, String t) {
+        if(s==null && t==null) return true;
+        if(s==null || t==null) return false;
+        if(s.length() != t.length()) return false;
+
+
+        HashMap<Character, Character> sMap= new HashMap<>();
+        HashSet<Character> set = new HashSet<>();
+
+        for(int i=0; i<s.length(); i++){
+            char sChar= s.charAt(i);
+            char tChar = t.charAt(i);
+            if(sMap.containsKey(sChar)){
+                if(sMap.get(sChar)!=tChar) return false;
+            } else{
+                if(set.contains(tChar)) return false;
+                set.add(tChar);
+                sMap.put(sChar,tChar);
+            }
+        }
+        return true;
+    }
+
+
+    public static void main(String args[]) {
+        Problem1 problem1 = new Problem1();
+        String s= "bba";
+        String t= "aad";
+        System.out.println("isomorphic "+problem1.isIsomorphic(s,t));
+
+    }
+}

Problem2.java

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+// Time Complexity :isIsomorphic: O(2n)=O(n) , n is  number of characters in the string
+// Space Complexity :0(1)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this : nothing
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+
+public class Problem2 {
+    public List<List<String>> groupAnagrams(String[] strs) {
+        HashMap<Double, List<String>> map = new HashMap<>();
+
+        for (String str : strs){
+            double hash = getHash(str);
+            if(!map.containsKey(hash)){
+                map.put(hash,new ArrayList<>());
+            }
+                map.get(hash).add(str);
+
+        }
+
+        return new ArrayList<>(map.values());
+    }
+
+    private double getHash(String str){
+        int hash = 1;
+        int[] prime ={ 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101};
+        for( char c : str.toCharArray()){
+            hash = hash * prime[c-'a'];
+        }
+        return hash;
+    }
+
+    public static void main(String args[]) {
+            Problem2 problem2= new Problem2();
+        String[] s= {"eat","tea","tan","ate","nat","bat"};
+        System.out.println("grouped anagram is "+problem2.groupAnagrams(s));
+
+    }
+}

Problem3.java

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+// Time Complexity :wordPattern: O(2n)=O(n) , n is  number of characters in the string
+// Space Complexity :0(n)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this : nothing
+
+import java.util.HashMap;
+import java.util.HashSet;
+
+public class Problem3 {
+    public boolean wordPattern(String pattern, String s) {
+        String[] words = s.split(" ");
+        if(pattern.length() != words.length) return false;
+        HashMap<Character,String> map= new HashMap<>();
+        HashSet<String> set = new HashSet<>();
+
+        for(int i=0; i<pattern.length(); i++){
+            char pChar = pattern.charAt(i);
+            if(map.containsKey(pChar)){
+                if(!map.get(pChar).equals(words[i])) return false;
+            } else{
+                if(set.contains(words[i])) return false;
+                set.add(words[i]);
+                map.put(pChar,words[i]);
+            }
+        }
+        return true;
+    }
+
+    public static void main(String args[]) {
+        Problem3 problem3= new Problem3();
+        String pattern= "abba";
+        String s= "dog dog dog dog";
+        System.out.println("pattern match found "+problem3.wordPattern(pattern,s));
+
+    }
+}