Group Anagrams

Author: forest000014

group-anagrams/forest000014.java

@@ -0,0 +1,39 @@
+/*
+Time Complexity: O(n)
+Space Complexity: O(n)
+*/
+class Solution {
+    public List<List<String>> groupAnagrams(String[] strs) {
+        Map<String, List<String>> map = new HashMap<>();
+
+        for (String str : strs) {
+            int[] cnt = new int[26];
+            for (int i = 0; i < str.length(); i++) {
+                cnt[str.charAt(i) - 'a']++;
+            }
+            char[] chars = new char[str.length()];
+            int idx = 0;
+            for (int i = 0; i < 26; i++) {
+                while (cnt[i] > 0) {
+                    chars[idx++] = (char)(i + 'a');
+                    cnt[i]--;
+                }
+            }
+            String sorted = new String(chars);
+            if (!map.containsKey(sorted)) {
+                map.put(sorted, new ArrayList<>());
+            }
+            map.get(sorted).add(str);
+        }
+
+        List<List<String>> ans = new ArrayList<>();
+        for (String key : map.keySet()) {
+            ans.add(new ArrayList<>());
+            for (String str : map.get(key)) {
+                ans.get(ans.size() - 1).add(str);
+            }
+        }
+
+        return ans;
+    }
+}