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…

You are given a list of users, each with a start time and an end time.For each time interval where the set of active users changes, output: Input Example Output Example Convert all start/end into events: Sort events and sweep from left to right.Maintain an active user set: Between consecutive event times, output a time…

Given a log file, find the top N most talkative users Parse each line, extract username and message, count words, aggregate per user in a map, sort by total word count (desc), return top N. Given a chat log, count how many words each user has spoken and return the top N most talkative users….

You have a list of meetings in your calendar with a start and end time. You are very busy, so meetings can overlap. You also have one “Do Not Schedule”(DNS) interval during which you don’t attend any meeting. Any meeting schedule that overlaps with a DNS slot is automatically cut such that it does not…