Refine comments and time complexity in Accounts Merge

Updated comments and time complexity analysis in the code.

Author: 724thomas

leetcode3/최원준/721. Accounts Merge.py

@@ -0,0 +1,46 @@
+#
+
+'''
+1. 아이디어 :
+dictionary 하나로는 같은 key가 존재하여 관리가 안됩니다.
+key: [set1, set2, ...]식으로 관리를 합니다.
+
+2. 시간복잡도 :
+    O(1000 * (10 + 1000))
+
+3. 자료구조/알고리즘 :
+dict, set
+
+'''
+from collections import defaultdict
+class Solution:
+    def accountsMerge(self, accounts: List[List[str]]) -> List[List[str]]:
+        map = defaultdict(list)
+        
+        for account in accounts:
+            name = account[0]
+            emails = set(account[1:])
+
+            overlap_set = []
+            
+            for email_set in map[name]:
+                if emails & email_set:
+                    overlap_set.append(email_set)
+            
+            if not overlap_set:
+                map[name].append(emails)
+                continue
+            
+            for email_set in overlap_set:
+                emails.update(email_set)
+                map[name].remove(email_set)
+            
+            map[name].append(emails)
+        
+        ans = []
+        for name, email_sets in map.items():
+            for email_set in email_sets:
+                ans.append([name] + sorted(email_set))
+        
+        return ans
+