Create Count Mentions Per User.java

varunu28 · web-flow · commit 4c9aa9825459 · 2025-01-31T08:19:14.000-08:00
diff --git a/Medium/Count Mentions Per User.java b/Medium/Count Mentions Per User.java
@@ -0,0 +1,61 @@
+class Solution {
+    public int[] countMentions(int numberOfUsers, List<List<String>> eventLog) {
+        List<Event> events = eventLog.stream()
+            .map(Event::buildEvent)
+            .sorted()
+            .collect(Collectors.toList());
+        Map<Integer, Integer> offlineUsers = new HashMap<>();
+        int[] mentions = new int[numberOfUsers];
+        for (Event event : events) {
+            if (event.message().equals("OFFLINE")) {
+                offlineUsers.put(Integer.parseInt(event.mentionString()), event.timestamp());
+            } else {
+                int timestamp = event.timestamp();
+                List<Integer> onlineUsers = offlineUsers.entrySet()
+                    .stream()
+                    .filter(t -> timestamp - t.getValue() >= 60)
+                    .map(Map.Entry::getKey)
+                    .collect(Collectors.toList());
+                onlineUsers.forEach(offlineUsers::remove);
+                String mentionString = event.mentionString();
+                if (mentionString.equals("ALL")) {
+                    for (int i = 0; i < numberOfUsers; i++) {
+                        mentions[i]++;
+                    }
+                } else if (mentionString.equals("HERE")) {
+                    for (int i = 0; i < numberOfUsers; i++) {
+                        if (!offlineUsers.containsKey(i)) {
+                            mentions[i]++;
+                        }
+                    }
+                } else {
+                    String[] usersMentioned = mentionString.split(" ");
+                    for (String user : usersMentioned) {
+                        int userId = Integer.parseInt(user.substring(2));
+                        mentions[userId]++;
+                    }
+                }
+            }
+        }
+        return mentions;
+    }
+
+    private record Event(String message, int timestamp, String mentionString) implements Comparable<Event> {
+
+        public static Event buildEvent(List<String> event) {
+            String message = event.get(0);
+            int timestamp = Integer.parseInt(event.get(1));
+            String mentionString = event.get(2);
+            return new Event(message, timestamp, mentionString);
+        }
+
+        @Override
+        public int compareTo(Event o) {
+            int c = this.timestamp - o.timestamp;
+            if (c != 0) {
+                return c;
+            }
+            return o.message().compareTo(this.message());
+        }
+    }
+}
