Given the head of a linked list, return the node where the cycle begins. If there is no cycle, return null.
There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the next pointer. Internally, pos is used to denote the index of the node that tail’s next pointer is connected to (0-indexed). It is -1 if there is no cycle. Note that pos is not passed as a parameter.
Do not modify the linked list.
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. In a normal queue, once the queue becomes full, we cannot insert the next element even if there is a space in front of the queue. But using the circular queue, we can use the space to store new values.
Implementation the MyCircularQueue class:
- MyCircularQueue(k) Initializes the object with the size of the queue to be k.
- int Front() Gets the front item from the queue. If the queue is empty, return -1.
- int Rear() Gets the last item from the queue. If the queue is empty, return -1.
- boolean enQueue(int value) Inserts an element into the circular queue. Return true if the operation is successful.
- boolean deQueue() Deletes an element from the circular queue. Return true if the operation is successful.
- boolean isEmpty() Checks whether the circular queue is empty or not.
- boolean isFull() Checks whether the circular queue is full or not.
You must solve the problem without using the built-in queue data structure in your programming language.
201. Bitwise AND of Numbers Range
Given two integers left and right that represent the range [left, right], return the bitwise AND of all numbers in this range, inclusive.
719. Find K-th Smallest Pair Distance
The distance of a pair of integers a and b is defined as the absolute difference between a and b.
Given an integer array nums and an integer k, return the kth smallest distance among all the pairs nums[i] and nums[j] where 0 <= i < j < nums.length.
1874. Minimize Product Sum of Two Arrays
The product sum of two equal-length arrays a and b is equal to the sum of a[i] * b[i] for all 0 <= i < a.length (0-indexed).
- For example, if a = [1,2,3,4] and b = [5,2,3,1], the product sum would be 1 x 5 + 2 x 2 + 3 x 3 + 4 x 1 = 22.
Given two arrays nums1 and nums2 of length n, return the minimum product sum if you are allowed to rearrange the order of the elements in nums1.
703. Kth Largest Element in a Stream
Design a class to find the kth largest element in a stream. Note that it is the kth largest element in the sorted order, not the kth distinct element.
Implement KthLargest class:
- KthLargest(int k, int[] nums) Initializes the object with the integer k and the stream of integers nums.
- int add(int val) Appends the integer val to the stream and returns the element representing the kth largest element in the stream.
1797. Design Authentication Manager
There is an authentication system that works with authentication tokens. For each session, the user will receive a new authentication token that will expire timeToLive seconds after the currentTime. If the token is renewed, the expiry time will be extended to expire timeToLive seconds after the (potentially different) currentTime.
Implement the AuthenticationManager class:
- AuthenticationManager(int timeToLive) constructs the AuthenticationManager and sets the timeToLive.
- generate(string tokenId, int currentTime) generates a new token with the given tokenId at the given currentTime in seconds.
- renew(string tokenId, int currentTime) renews the unexpired token with the given tokenId at the given currentTime in seconds. If there are no unexpired tokens with the given tokenId, the request is ignored, and nothing happens.
- countUnexpiredTokens(int currentTime) returns the number of unexpired tokens at the given currentTime.
Note that if a token expires at time t, and another action happens on time t (renew or countUnexpiredTokens), the expiration takes place before the other actions.