Parentheses strings are strings containing only the characters ‘(‘ and ‘)’.A parentheses string is considered balanced when its opening parentheses align with its closing parentheses.For example, “()” and “(())” are balanced, while “)(“, “())(” are not. Given a string consisting of the same number of opening and closing parentheses, determine the minimum number of character…

You are running a car dealership and currently have 2 employees.We are going to be building a basic function to deal with customers booking appointments with your employees. You have the following constraints: Implement a DealershipScheduler class with the following method: Return true if you can book an appointment for these times, and false if…

You’re building a daily calendar app and need to display all of the day’s events in the right location on the screen, but it needs to be given a bounding box.We need to take a list of events happening that day and produce a list of bounding boxes to be drawn. An event has: Example…

Problem statement（题目原文）Given: What is the result of each of the following statements? Brief idea Know == performs coercion (string → number), === doesn’t; + concatenates when a string is involved; unary + coerces to number. The VOprep team has long accompanied candidates through various major company OAs and VOs, including Microsoft Google, Amazon, Citadel, SIG, providing real-time…

Problem statementImagine you’re working on a language which only supports Stack, but you need a Queue functionality to fulfill the requirement. Design a queue that supports standard operations using stacks. Brief idea (EN)Use two stacks: in and out. The VOprep team has long accompanied candidates through various major company OAs and VOs, including Microsoft Google, Amazon, Citadel,…

Design a simulation for a card game. This game is playable by 2 or more playersand consists of four phases performed in order: shuffle, deal, exchange, and score. Deck of cards: The VOprep team has long accompanied candidates through various major company OAs and VOs, including Microsoft Google, Amazon, Citadel, SIG, providing real-time voice assistance, remote practice,…

Description The 8 Puzzle is a sliding block game played on a 3×3 grid containing 8 numbered tiles (from 1 to 8) and one empty space represented by 0. The objective is to rearrange the tiles into a specific goal configuration by sliding them one at a time.Only tiles adjacent to the empty space (0)…

An integer array “original” is transformed into a doubled array “changed” by appending twice the value of every element in “original”, and then randomly shuffling the resulting array.Given an array “changed”, return “original” if “changed” is a doubled array. If “changed” is not a doubled array, return an empty array. The elements in “original” may…

Given an array nums with n integers, your task is to check if it could become non-decreasing by modifying at most one element.We define an array as non-decreasing if nums[i] <= nums[i+1] holds for every i (0-based) such that 0 <= i <= n-2. English Summary (Approach)Single pass. Count violations where nums[i] > nums[i+1]. If…

Find the unique element in an array where all elements appear twice except one.Examples: Summary (with approach)Use XOR: since a ^ a = 0, a ^ 0 = a, and XOR is associative/commutative, XOR all numbers; the result is the single number. Runs in O(N) time and O(1) space. Alternative: hash counting in O(N) space….

Imagine an array that contains both integers and nested arrays, such as the following:[8, 4, [5, [9], 3], 6].The depth sum is described as the weighted sum of each integer, weighted by their respective depths. In the example, 8’s depth is 1, while 9’s is 3.Given such an array, calculate its depth sum. Examples Summary…

You are given K sorted integer arrays (non-decreasing). Arrays may contain duplicates within the same array and across different arrays.Return a sorted list of unique integers that appear in any of the arrays (i.e., the set union, sorted). Example:A = [-100, -1, -1, 0, 5]B = [0]C = [-1, 0, 0]Output → [-100, -1, 0,…

Given the root of a binary search tree, return a balanced binary search tree that contains the same node values. If there is more than one valid answer, return any of them.A binary search tree is balanced if the depth of the two subtrees of every node never differs by more than 1. Example:Input: root…

Problem (English original):Given the root of a binary tree containing integers, return a list of all the integers in the tree ordered by column from left to right. Within each column, values should be ordered from top to bottom. Assume a node definition (or language equivalent): Input (example, ASCII tree): Output (example): Summary (approach):BFS/DFS tagging…

Given a string S consisting of lowercase English characters, determine if you can make it a palindrome by removing at most one character. Example: Summary (approach):Use two pointers. On the first mismatch, try skipping either the left or the right character and check if the remaining substring is a palindrome. O(n) time, O(1) space. The VOprep team…

Problem (verbatim):“A multiset (also known as a bag) is a mutable, unordered collection of distinct objects that may appear more than once in the collection. Implement a multiset that implements the following methods:• add(element)• remove(element)• count(for: element)” English summary (concise approach):Back the multiset with a hash map value → frequency. The VOprep team has long accompanied candidates…

Problem (verbatim):“Given an integer array and an integer number k. Return the k-th largest element in the array. Examples:• array = [5, −3, 9, −1]• k = 0 ⇒ return: 9• k = 1 ⇒ return: 5• k = 3 ⇒ return: −3” summary (concise approach):Return the k-th largest (0-indexed) value. The VOprep team has long accompanied…

Problem Statement (English original)Assume a binary-tree node: Given the root of a binary tree, output the node values in vertical order (column order) from leftmost column to rightmost column.Within each column, list nodes top-to-bottom in the order they are encountered by a standard BFS (or by row index if you compute coordinates). Illustrative example (matching…

Problem Statement (English original)You are given a current working directory cwd (an absolute Unix-style path) and a cd(arg) string which can be either an absolute path (starts with /) or a relative path (may include segments . and ..).Implement a function that returns the normalized absolute path after applying cd(arg) from cwd. Rules: Examples (from…

You are given a 2-D grid representing two elevators (left elevator A, right elevator B).Each cell may contain a digit representing the number of people waiting on that floor for that elevator. Example grid: Legend: You are also given a query describing a request: Task Given the grid and a request in the format: Write…