upd

algorithms/labs/lab8/code/hash/1.py

@@ -0,0 +1,60 @@
+class Node:
+    def __init__(self, key, val):
+        self.key = key
+        self.val = val
+        self.prev = None
+        self.next = None
+
+
+class LRUCache:
+    def __init__(self, capacity: int):
+        self.cap = capacity
+        self.cache = {}
+        self.left = Node(0, 0)
+        self.right = Node(0, 0)
+        self.left.next = self.right
+        self.right.prev = self.left
+
+    def remove(self, node):
+        p, n = node.prev, node.next
+        p.next = n
+        n.prev = p
+
+    def insert(self, node):
+        p, n = self.right.prev, self.right
+        p.next = node
+        node.prev = p
+        node.next = n
+        n.prev = node
+
+    def get(self, key: int) -> int:
+        if key not in self.cache:
+            return -1
+        node = self.cache[key]
+        self.remove(node)
+        self.insert(node)
+        return node.val
+
+    def put(self, key: int, value: int) -> None:
+        if key in self.cache:
+            self.remove(self.cache[key])
+        node = Node(key, value)
+        self.cache[key] = node
+        self.insert(node)
+        if len(self.cache) > self.cap:
+            lru = self.left.next
+            self.remove(lru)
+            del self.cache[lru.key]
+
+
+if __name__ == "__main__":
+    lru = LRUCache(2)
+    lru.put(1, 1)
+    lru.put(2, 2)
+    print(lru.get(1))
+    lru.put(3, 3)
+    print(lru.get(2))
+    lru.put(4, 4)
+    print(lru.get(1))
+    print(lru.get(3))
+    print(lru.get(4))

algorithms/labs/lab8/code/hash/2.py

@@ -0,0 +1,43 @@
+class TrieNode:
+    def __init__(self):
+        self.children = {}
+        self.is_end = False
+
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+
+    def insert(self, word):
+        node = self.root
+        for ch in word:
+            if ch not in node.children:
+                node.children[ch] = TrieNode()
+            node = node.children[ch]
+        node.is_end = True
+
+    def search(self, word):
+        node = self.root
+        for ch in word:
+            if ch not in node.children:
+                return False
+            node = node.children[ch]
+        return node.is_end
+
+    def startsWith(self, prefix):
+        node = self.root
+        for ch in prefix:
+            if ch not in node.children:
+                return False
+            node = node.children[ch]
+        return True
+
+
+if __name__ == "__main__":
+    t = Trie()
+    t.insert("apple")
+    print(t.search("apple"))
+    print(t.search("app"))
+    print(t.startsWith("app"))
+    t.insert("app")
+    print(t.search("app"))

algorithms/labs/lab8/code/hash/3.py

@@ -0,0 +1,50 @@
+import heapq
+
+
+class Twitter:
+    def __init__(self):
+        self.time = 0
+        self.tweets = {}
+        self.follows = {}
+
+    def postTweet(self, userId, tweetId):
+        self.time += 1
+        if userId not in self.tweets:
+            self.tweets[userId] = []
+        self.tweets[userId].append((-self.time, tweetId))
+
+    def getNewsFeed(self, userId):
+        heap = []
+        if userId in self.tweets:
+            heap.extend(self.tweets[userId][-10:])
+        if userId in self.follows:
+            for v in self.follows[userId]:
+                if v in self.tweets:
+                    heap.extend(self.tweets[v][-10:])
+        heapq.heapify(heap)
+        res = []
+        while heap and len(res) < 10:
+            res.append(heapq.heappop(heap)[1])
+        return res
+
+    def follow(self, followerId, followeeId):
+        if followerId == followeeId:
+            return
+        if followerId not in self.follows:
+            self.follows[followerId] = set()
+        self.follows[followerId].add(followeeId)
+
+    def unfollow(self, followerId, followeeId):
+        if followerId in self.follows and followeeId in self.follows[followerId]:
+            self.follows[followerId].remove(followeeId)
+
+
+if __name__ == "__main__":
+    tw = Twitter()
+    tw.postTweet(1, 5)
+    print(tw.getNewsFeed(1))
+    tw.follow(1, 2)
+    tw.postTweet(2, 6)
+    print(tw.getNewsFeed(1))
+    tw.unfollow(1, 2)
+    print(tw.getNewsFeed(1))