Add solution #3433

JoshCrozier · JoshCrozier · commit 09354effd9b8 · 2025-12-11T21:02:13.000-06:00
diff --git a/README.md b/README.md
@@ -2750,6 +2750,7 @@
 3423|[Maximum Difference Between Adjacent Elements in a Circular Array](./solutions/3423-maximum-difference-between-adjacent-elements-in-a-circular-array.js)|Easy|
 3431|[Minimum Unlocked Indices to Sort Nums](./solutions/3431-minimum-unlocked-indices-to-sort-nums.js)|Medium|
 3432|[Count Partitions with Even Sum Difference](./solutions/3432-count-partitions-with-even-sum-difference.js)|Easy|
+3433|[Count Mentions Per User](./solutions/3433-count-mentions-per-user.js)|Medium|
 3437|[Permutations III](./solutions/3437-permutations-iii.js)|Medium|
 3439|[Reschedule Meetings for Maximum Free Time I](./solutions/3439-reschedule-meetings-for-maximum-free-time-i.js)|Medium|
 3440|[Reschedule Meetings for Maximum Free Time II](./solutions/3440-reschedule-meetings-for-maximum-free-time-ii.js)|Medium|
diff --git a/solutions/3433-count-mentions-per-user.js b/solutions/3433-count-mentions-per-user.js
@@ -0,0 +1,74 @@
+/**
+ * 3433. Count Mentions Per User
+ * https://leetcode.com/problems/count-mentions-per-user/
+ * Difficulty: Medium
+ *
+ * You are given an integer numberOfUsers representing the total number of users and an
+ * array events of size n x 3.
+ *
+ * Each events[i] can be either of the following two types:
+ * 1. Message Event: ["MESSAGE", "timestampi", "mentions_stringi"]
+ *   - This event indicates that a set of users was mentioned in a message at timestampi.
+ *   - The mentions_stringi string can contain one of the following tokens:
+ *     - id<number>: where <number> is an integer in range [0,numberOfUsers - 1]. There can
+ *       be multiple ids separated by a single whitespace and may contain duplicates. This
+ *       can mention even the offline users.
+ *     - ALL: mentions all users.
+ *     - HERE: mentions all online users.
+ * 2. Offline Event: ["OFFLINE", "timestampi", "idi"]
+ * - This event indicates that the user idi had become offline at timestampi for 60 time units.
+ *   The user will automatically be online again at time timestampi + 60.
+ *
+ * Return an array mentions where mentions[i] represents the number of mentions the user with
+ * id i has across all MESSAGE events.
+ *
+ * All users are initially online, and if a user goes offline or comes back online, their status
+ * change is processed before handling any message event that occurs at the same timestamp.
+ *
+ * Note that a user can be mentioned multiple times in a single message event, and each mention
+ * should be counted separately.
+ */
+
+/**
+ * @param {number} numberOfUsers
+ * @param {string[][]} events
+ * @return {number[]}
+ */
+var countMentions = function(numberOfUsers, events) {
+  const result = new Array(numberOfUsers).fill(0);
+  const onlineAt = new Array(numberOfUsers).fill(0);
+
+  events.sort((a, b) => {
+    const timeCompare = parseInt(a[1], 10) - parseInt(b[1], 10);
+    if (timeCompare !== 0) return timeCompare;
+    return a[0] === 'MESSAGE' ? 1 : -1;
+  });
+
+  for (const [type, timestampStr, data] of events) {
+    const timestamp = parseInt(timestampStr, 10);
+
+    if (type === 'OFFLINE') {
+      const userId = parseInt(data, 10);
+      onlineAt[userId] = timestamp + 60;
+    } else {
+      if (data === 'ALL') {
+        for (let i = 0; i < numberOfUsers; i++) {
+          result[i]++;
+        }
+      } else if (data === 'HERE') {
+        for (let i = 0; i < numberOfUsers; i++) {
+          if (onlineAt[i] <= timestamp) {
+            result[i]++;
+          }
+        }
+      } else {
+        const ids = data.replace(/id/g, '').split(' ');
+        for (const id of ids) {
+          result[parseInt(id, 10)]++;
+        }
+      }
+    }
+  }
+
+  return result;
+};
