Design and implement a data structure for Least Frequently Used (LFU) cache. It should support the following operations: get and put. get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1. put(key, value) - Set or insert the value if the key is not already present. When the cache reaches its capacity, it should invalidate the least frequently used item before inserting a new item.
Design a HashMap without using any built-in hash table libraries. To be specific, your design should include these functions: put(key, value): Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value. get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key. remove(key): Remove the mapping for the value key if this map contains the mapping for the key.
Design your implementation of the circular double-ended queue (deque). Your implementation should support following operations: MyCircularDeque(k): Constructor, set the size of the deque to be k. insertFront(): Adds an item at the front of Deque. Return true if the operation is successful. insertLast(): Adds an item at the rear of Deque. Return true if the operation is successful. deleteFront(): Deletes an item from the front of Deque. Return true if the operation is successful.
Design a HashSet without using any built-in hash table libraries. To be specific, your design should include these functions: add(value): Insert a value into the HashSet. contains(value): Return whether the value exists in the HashSet or not. remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing. Example MyHashSet hashSet = new MyHashSet(); hashSet.add(1); hashSet.add(2); hashSet.contains(1); // returns true hashSet.contains(3); // returns false (not found) hashSet.
Design and implement an iterator to flatten a 2d vector. It should support the following operations: next and hasNext. Example Vector2D iterator = new Vector2D([[1,2],[3],[4]]); iterator.next(); // return 1 iterator.next(); // return 2 iterator.next(); // return 3 iterator.hasNext(); // return true iterator.hasNext(); // return true iterator.next(); // return 4 iterator.hasNext(); // return false Notes Please remember to RESET your class variables declared in Vector2D, as static/class variables are persisted across multiple test cases.
A character in UTF8 can be from 1 to 4 bytes long, subjected to the following rules: For 1-byte character, the first bit is a 0, followed by its unicode code. For n-bytes character, the first n-bits are all one’s, the n+1 bit is 0, followed by n-1 bytes with most significant 2 bits being 10. This is how the UTF-8 encoding would work: Char. number range | UTF-8 octet sequence (hexadecimal) | (binary) --------------------+--------------------------------------------- 0000 0000-0000 007F | 0xxxxxxx 0000 0080-0000 07FF | 110xxxxx 10xxxxxx 0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx 0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx Given an array of integers representing the data, return whether it is a valid utf-8 encoding.
Design your implementation of the circular queue. The circular queue is a linear data structure in which the operations are performed based on FIFO (First In First Out) principle and the last position is connected back to the first position to make a circle. It is also called “Ring Buffer”. One of the benefits of the circular queue is that we can make use of the spaces in front of the queue.
Given a stream of integers and a window size, calculate the moving average of all integers in the sliding window. Example MovingAverage m = new MovingAverage(3); m.next(1) = 1 m.next(10) = (1 + 10) / 2 m.next(3) = (1 + 10 + 3) / 3 m.next(5) = (10 + 3 + 5) / 3 Solution from collections import deque class MovingAverage: def __init__(self, size: int): """ Initialize your data structure here.
Design a logger system that receive stream of messages along with its timestamps, each message should be printed if and only if it is not printed in the last 10 seconds. Given a message and a timestamp (in seconds granularity), return true if the message should be printed in the given timestamp, otherwise returns false. It is possible that several messages arrive roughly at the same time. Example Logger logger = new Logger(); // logging string "foo" at timestamp 1 logger.
Design a hit counter which counts the number of hits received in the past 5 minutes. Each function accepts a timestamp parameter (in seconds granularity) and you may assume that calls are being made to the system in chronological order (ie, the timestamp is monotonically increasing). You may assume that the earliest timestamp starts at 1. It is possible that several hits arrive roughly at the same time. Example HitCounter counter = new HitCounter(); // hit at timestamp 1.