feat : group-anagrams

Author: ekgns33

group-anagrams/ekgns33.java

@@ -0,0 +1,45 @@
+/**
+
+ input : array of strings
+ output : grouped anagrams
+
+ ex) eat ate tea > same group
+
+ solution 1) brute force
+ ds : hashmap
+ algo : sort
+ generate Key by sorting string O(nlogn)
+
+ save to hashmap
+
+ tc : O(m* nlogn) when m is length of array, n is max length of string
+ sc : O(m)
+
+ solutino 2) better?
+ cannot optimize m times read
+ how about generating key
+
+ sort = nlogn
+ read = n << use frequency
+ 26 * n
+ tc : O(m * (26 * n)) ~= O(mn)
+ sc : O(m * 26) ~= O(m)
+ */
+
+class Solution {
+  public List<List<String>> groupAnagrams(String[] strs) {
+    Map<String, List<String>> map = new HashMap<>();
+    int n = strs.length;
+    for(String str : strs) {
+      int l = str.length();
+      char[] freq = new char[26];
+      for(int i = 0; i < l; i++) {
+        freq[str.charAt(i) - 'a']++;
+      }
+      String key = new String(freq);
+      map.putIfAbsent(key, new ArrayList<>());
+      map.get(key).add(str);
+    }
+    return List.copyOf(map.values());
+  }
+}