[20250906] PGM / LV3 / 불량 사용자 / 김수연

[20250906] PGM / LV3 / 불량 사용자 / 김수연

Author: suyeun84

suyeun84/202509/06 PGM LV3 불량 사용자.md

@@ -0,0 +1,37 @@
+```java
+import java.util.*;
+class Solution {
+    public int solution(String[] user_id, String[] banned_id) {
+        HashSet<HashSet<String>> result = new HashSet<>();
+        
+        dfs(new HashSet<>(), user_id, banned_id, result);
+        return result.size();
+    }
+    
+    private void dfs(HashSet<String> hashset, String[] user_id, String[] banned_id, HashSet<HashSet<String>> result) {
+        if (hashset.size() == banned_id.length) {
+            result.add(new HashSet<>(hashset));
+            return;
+        };
+        String target = banned_id[hashset.size()];
+        
+        for (String user : user_id) {
+            if (hashset.contains(user)) continue;
+            if (check(target, user)) {
+                hashset.add(user);
+                dfs(hashset, user_id, banned_id, result);
+                hashset.remove(user);
+            }
+        }
+    }
+    private boolean check(String target, String user) {
+        if (target.length() != user.length()) return false;
+        for (int j = 0; j < target.length(); j++) {
+            if (target.charAt(j) == ('*')) continue;
+            if (target.charAt(j) == user.charAt(j)) continue;
+            return false;
+        }
+        return true;
+    }
+}
+```