https://leetcode.cn/problems/design-twitter/

Author: masx200

README.md

@@ -842,6 +842,8 @@ https://leetcode.cn/problems/different-ways-to-add-parentheses/
 
 https://leetcode.cn/problems/1-bit-and-2-bit-characters/
 
+https://leetcode.cn/problems/design-twitter/
+
 #### 安装教程
 
 1. 安装`deno`

design-twitter/index.ts

@@ -0,0 +1,64 @@
+export default class Twitter {
+    #time = 0;
+    #follower_to_followees: Map<number, Set<number>> = new Map();
+
+    #user_to_tweets: Map<number, Set<number>> = new Map();
+    #tweet_to_time = new Map<number, number>();
+    constructor() {}
+    #deleteTweet(userId: number, tweetId: number): void {
+        const tweets = this.#user_to_tweets.get(userId);
+        if (tweets) {
+            tweets.delete(tweetId);
+        }
+
+        this.#tweet_to_time.delete(tweetId);
+    }
+    postTweet(userId: number, tweetId: number): void {
+        const time = this.#time;
+        this.#tweet_to_time.set(tweetId, time);
+        const tweets = this.#user_to_tweets.get(userId) ?? new Set();
+        tweets.add(tweetId);
+        this.#user_to_tweets.set(userId, tweets);
+        this.#time++;
+
+        if (tweets.size > 10) {
+            const oldestTweet = tweets.values().next().value;
+            this.#deleteTweet(userId, oldestTweet);
+        }
+    }
+
+    getNewsFeed(userId: number): number[] {
+        const followees = this.#follower_to_followees.get(userId);
+        const tweets = Array.from(this.#user_to_tweets.get(userId) ?? []);
+        if (followees) {
+            for (const followee of followees) {
+                const userTweets = this.#user_to_tweets.get(followee);
+                if (userTweets) {
+                    userTweets.forEach((tweet) => tweets.push(tweet));
+                }
+            }
+        }
+
+        const sortedTweets = tweets
+            .sort((a, b) => {
+                const timeA = this.#tweet_to_time.get(a) ?? 0;
+                const timeB = this.#tweet_to_time.get(b) ?? 0;
+                return timeB - timeA;
+            })
+            .slice(0, 10);
+
+        return sortedTweets;
+    }
+
+    follow(followerId: number, followeeId: number): void {
+        const followee =
+            this.#follower_to_followees.get(followerId) ?? new Set();
+
+        followee.add(followeeId);
+        this.#follower_to_followees.set(followerId, followee);
+    }
+
+    unfollow(followerId: number, followeeId: number): void {
+        this.#follower_to_followees.get(followerId)?.delete(followeeId);
+    }
+}