You are given an array changed, which may have been created by doubling each element of an original array and then shuffling the elements. Your task is to determine if changed can be converted back into the original array, where each element in the original array has its double present in changed. If changed is not a valid doubled array, return an empty array. If it is valid, return the original array.
You are driving a taxi along a road with n points. Each point represents a location on the road. Passengers request rides from one point to another, and for each ride, you earn the distance traveled plus a tip. Your goal is to maximize your earnings by picking up passengers optimally. You can only carry one passenger at a time, and may pick up a new passenger at any point after dropping off the previous one.
You are given a stream of 2D points on the XY-plane. Your task is to design an algorithm that adds new points into a data structure and counts how many sets of three points, along with a given query point, can form an axis-aligned square. An axis-aligned square is a square where the edges are parallel or perpendicular to the X-axis and Y-axis, with all sides of equal length.
You are given an array of digit strings nums and a target digit string target. Count the number of valid pairs of indices (i, j) where i != j such that the concatenation of nums[i] and nums[j] equals target.
You are given a stream of stock price records, where each record contains a timestamp and the corresponding price of the stock. The records may not be in order, and some records may contain errors that need to be corrected. Your task is to design an algorithm that updates the stock price at a given timestamp, finds the current price at the latest timestamp, and also finds the maximum and minimum prices the stock has been based on the current records.
You are required to build a system for a bank that automates various account transactions, including deposits, withdrawals, and transfers. The bank has multiple accounts, and each transaction must adhere to specific rules to be considered valid. Implement a class that handles these operations efficiently while ensuring transactional integrity.