355_Design_Twitter

Author: partho-maple

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/355_Design_Twitter.swift

@@ -0,0 +1,60 @@
+import Foundation
+
+class Twitter {
+
+    var userIDAndTweetMap = [Int:[(Int, Int)]]()
+    var followerAndfolloweeMap = [Int:Set<Int>]() // [follower: Set<followee>]
+    let maxPost = 10
+    var currentTimeRef = 10000
+    
+    init() {
+        
+    }
+    
+    func postTweet(_ userId: Int, _ tweetId: Int) {
+        currentTimeRef += 1
+        
+        // add tweet to user's feed
+        userIDAndTweetMap[userId, default: [(Int, Int)]()].append((tweetId, currentTimeRef))
+        if userIDAndTweetMap[userId]!.count > maxPost {
+            userIDAndTweetMap[userId]!.removeFirst()
+        }
+    }
+    
+    func getNewsFeed(_ userId: Int) -> [Int] {
+        var allFeeds = [(Int, Int)]()
+        
+        if let feeds = userIDAndTweetMap[userId] {
+            allFeeds.append(contentsOf: feeds)
+        }
+        
+        if let followeeIds = followerAndfolloweeMap[userId] {
+            for followeeId in Array(followeeIds) {
+                if let feeds = userIDAndTweetMap[followeeId] {
+                    allFeeds.append(contentsOf: feeds)
+                }
+            }
+        }
+        allFeeds.sort { $0.1 > $1.1 }
+        let feeds = allFeeds.map { $0.0 }
+        
+        return feeds.count <= maxPost ? feeds : Array(feeds[0..<10])
+    }
+    
+    func follow(_ followerId: Int, _ followeeId: Int) {
+        followerAndfolloweeMap[followerId, default: Set<Int>()].insert(followeeId)
+    }
+    
+    func unfollow(_ followerId: Int, _ followeeId: Int) {
+        followerAndfolloweeMap[followerId]?.remove(followeeId)
+    }
+}
+
+/**
+ * Your Twitter object will be instantiated and called as such:
+ * let obj = Twitter()
+ * obj.postTweet(userId, tweetId)
+ * let ret_2: [Int] = obj.getNewsFeed(userId)
+ * obj.follow(followerId, followeeId)
+ * obj.unfollow(followerId, followeeId)
+ */