feat: group anagrams

Author: std-freejia

group-anagrams/std-freejia.java

@@ -0,0 +1,23 @@
+class Solution {
+    public List<List<String>> groupAnagrams(String[] strs) {
+        List<List<String>> answer = new ArrayList<>();
+        // <정렬한 문자, 원본 문자 리스트>
+        HashMap<String, List<String>> map = new HashMap<>();
+
+        for (String str : strs) {
+            char[] arr = str.toCharArray();
+            Arrays.sort(arr);
+            String strKey = String.valueOf(arr);
+            
+            if (!map.containsKey(strKey)) {
+                ArrayList<String> list = new ArrayList<>();
+                list.add(str);
+                map.put(strKey, list);
+            } else {
+                map.get(strKey).add(str);
+            }
+        }
+        answer.addAll(map.values());
+        return answer;
+    }
+}