Citadel Interview Questions

You're given two arrays. Construct the longest possible non-decreasing subarray by picking elements from either array at each index.

Find the minimum number of moves a knight needs to reach a target position on an infinite chessboard, starting from (0, 0).

Find the maximum sum of any path in a binary tree, where a path can start and end at any node. The path must contain at least one node.

Find the maximum value within a sliding window of size k as it moves across an array. You'll need to efficiently update the maximum as the window slides.

Find the number of palindromic substrings within a given string. Consider each single character and repeated characters as a substring.

The problem asks you to find the total number of distinct palindromic subsequences within a given string. Remember that subsequences don't have to be contiguous.

You're given a list of numbers. By deleting a number, you earn its value, but you must also delete all numbers one less and one greater than it. Maximize the total earned value.

You're given two arrays that contain zeros. Replace the zeros in each array with positive integers to maximize the chance of making the two arrays have equal sums. Find the minimum equal sum achievable or determine if it's impossible.

You're given a list of numbers. Determine the minimum number of operations to make all numbers non-positive by either subtracting or dividing them by a given value.

Design and implement a Least Frequently Used (LFU) cache. The cache should allow you to get and put key-value pairs, evicting the least frequently used key when the cache is full.

You're given a set of spells with damage and cost. Choose the subset of spells that maximizes your total damage, staying within a given mana limit.

You're given the costs of traveling between cities on a train line, with options to use regular tickets or purchase a travel pass for unlimited rides. Find the minimum total cost to travel to the last city.

Design a data structure that acts as a Least Recently Used (LRU) cache. Implement methods to get and put key-value pairs, evicting the least recently used entry when the cache is full.

You're given a set of delivery locations. Find the best spot to build a service center that minimizes the total distance to all locations.

Find the longest common subarray between two given arrays of integers. Return the length of this maximal repeated subarray.

You are given a matrix and a sequence of integers. Determine the index of the first integer in the sequence that results in a fully painted row or column in the matrix.

You are given equations represented by pairs of variables and their corresponding values. Your task is to evaluate queries based on these equations, determining the value of expressions if possible, or returning -1.0 if not.

Given an array of numbers where one number appears more than once, find the duplicate number. You should do this without modifying the original array and using only constant extra space.

You are given a binary tree. Devise a way to convert the tree into a string representation (serialize) and then reconstruct the tree from that string (deserialize).

You are given a collection of intervals. Merge all overlapping intervals into a single interval and return the result.