add group anagrams solution

Author: Tessa1217

group-anagrams/Tessa1217.java

@@ -0,0 +1,21 @@
+/**
+ * 문자열 배열 strs가 주어질 때 애너그램인 문자들끼리 묶어서 반환하세요.
+ */
+class Solution {
+    // 시간복잡도: O(n * L log L)
+    public List<List<String>> groupAnagrams(String[] strs) {
+        Map<String, List<String>> anagramMap = new HashMap<>();
+        for (String str : strs) {
+            char[] word = str.toCharArray();
+            Arrays.sort(word);
+            String sortedCharacter = String.valueOf(word);
+            if (!anagramMap.containsKey(sortedCharacter)) {
+                anagramMap.put(sortedCharacter, new ArrayList<>());
+            }
+            anagramMap.get(sortedCharacter).add(str);
+        }
+        return new ArrayList(anagramMap.values());
+    }
+
+}
+