Add solution #355

Author: JoshCrozier

README.md

@@ -251,6 +251,7 @@
 349|[Intersection of Two Arrays](./0349-intersection-of-two-arrays.js)|Easy|
 350|[Intersection of Two Arrays II](./0350-intersection-of-two-arrays-ii.js)|Easy|
 352|[Data Stream as Disjoint Intervals](./0352-data-stream-as-disjoint-intervals.js)|Hard|
+355|[Design Twitter](./0355-design-twitter.js)|Medium|
 367|[Valid Perfect Square](./0367-valid-perfect-square.js)|Easy|
 371|[Sum of Two Integers](./0371-sum-of-two-integers.js)|Medium|
 372|[Super Pow](./0372-super-pow.js)|Medium|

solutions/0355-design-twitter.js

@@ -0,0 +1,75 @@
+/**
+ * 355. Design Twitter
+ * https://leetcode.com/problems/design-twitter/
+ * Difficulty: Medium
+ *
+ * Design a simplified version of Twitter where users can post tweets, follow/unfollow another user,
+ * and is able to see the 10 most recent tweets in the user's news feed.
+ *
+ * Implement the Twitter class:
+ * - Twitter() Initializes your twitter object.
+ * - void postTweet(int userId, int tweetId) Composes a new tweet with ID tweetId by the user
+ *   userId. Each call to this function will be made with a unique tweetId.
+ * - List<Integer> getNewsFeed(int userId) Retrieves the 10 most recent tweet IDs in the user's news
+ *   feed. Each item in the news feed must be posted by users who the user followed or by the user
+ *   themself. Tweets must be ordered from most recent to least recent.
+ * - void follow(int followerId, int followeeId) The user with ID followerId started following the
+ *   user with ID followeeId.
+ * - void unfollow(int followerId, int followeeId) The user with ID followerId started unfollowing
+ *   the user with ID followeeId.
+ */
+
+
+var Twitter = function() {
+  this.tweets = [];
+  this.followers = new Map();
+};
+
+/**
+ * @param {number} userId
+ * @param {number} tweetId
+ * @return {void}
+ */
+Twitter.prototype.postTweet = function(userId, tweetId) {
+  this.tweets.unshift([userId, tweetId]);
+};
+
+/**
+ * @param {number} userId
+ * @return {number[]}
+ */
+Twitter.prototype.getNewsFeed = function(userId) {
+  const result = [];
+  for (let i = 0; i < this.tweets.length && result.length < 10; i++) {
+    const [user, tweet] = this.tweets[i] ?? [];
+    if (user === userId || (this.followers.get(userId) && this.followers.get(userId).has(user))) {
+      result.push(tweet);
+    }
+  }
+  return result;
+};
+
+/**
+ * @param {number} followerId
+ * @param {number} followeeId
+ * @return {void}
+ */
+Twitter.prototype.follow = function(followerId, followeeId) {
+  if (followerId !== followeeId) {
+    if (!this.followers.has(followerId)) {
+      this.followers.set(followerId, new Set());
+    }
+    this.followers.get(followerId).add(followeeId);
+  }
+};
+
+/**
+ * @param {number} followerId
+ * @param {number} followeeId
+ * @return {void}
+ */
+Twitter.prototype.unfollow = function(followerId, followeeId) {
+  if (this.followers.has(followerId)) {
+    this.followers.get(followerId).delete(followeeId);
+  }
+};