solves group anagrams

anishLearnsToCode · anishLearnsToCode · commit 9f2af59d761e · 2022-01-06T17:35:50.000+01:00
diff --git a/README.md b/README.md
@@ -49,6 +49,7 @@
 |  46  | [Permutations](https://leetcode.com/problems/permutations)                                                                                                |                                                                  [![Java](assets/java.png)](src/Permutations.java)                                                                   |                                                                                                                                   |
 |  47  | [Permutations II](https://leetcode.com/problems/permutations-ii)                                                                                          |                                                                 [![Java](assets/java.png)](src/PermutationsII.java)                                                                  |                                                                                                                                   |
 |  48  | [Rotate Image](https://leetcode.com/problems/rotate-image)                                                                                                |                                                                   [![Java](assets/java.png)](src/RotateImage.java)                                                                   |                                                                                                                                   |
+|  49  | [Group Anagrams](https://leetcode.com/problems/group-anagrams)                                                                                            |                                                                  [![Java](assets/java.png)](src/GroupAnagrams.java)                                                                  |                                                                                                                                   |
 |  53  | [Maximum SubArray](https://leetcode.com/problems/maximum-subarray)                                                                                        |                                 [![Java](assets/java.png)](src/MaximumSubArray.java) [![Python](assets/python.png)](python/maximum_sum_subarray.py)                                  |                                                                                                                                   |
 |  55  | [Jump Game](https://leetcode.com/problems/jump-game)                                                                                                      |                                                                    [![Java](assets/java.png)](src/JumpGame.java)                                                                     |                                                                                                                                   |
 |  58  | [Length of Last Word](https://leetcode.com/problems/length-of-last-word)                                                                                  |                                 [![Java](assets/java.png)](src/LengthOfLastWord.java) [![Python](assets/python.png)](python/length_of_last_word.py)                                  |                                                                                                                                   |
diff --git a/src/GroupAnagrams.java b/src/GroupAnagrams.java
@@ -0,0 +1,33 @@
+// https://leetcode.com/problems/group-anagrams
+// T: O(|words| * |words[i]|)
+// S: O(|words| * |words[i]|)
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class GroupAnagrams {
+    public List<List<String>> groupAnagrams(String[] words) {
+        final Map<String, List<String>> anagrams = new HashMap<>();
+        for (String word : words) {
+            final String signature = getSignature(word);
+            if (anagrams.containsKey(signature)) {
+                anagrams.get(signature).add(word);
+            } else {
+                List<String> list = new ArrayList<>();
+                list.add(word);
+                anagrams.put(signature, list);
+            }
+        }
+        return new ArrayList<>(anagrams.values());
+    }
+
+    private String getSignature(String string) {
+        final char[] array = new char[26];
+        for (int i = 0 ; i < string.length() ; i++) {
+            array[string.charAt(i) - 'a']++;
+        }
+        return String.valueOf(array);
+    }
+}
