A happy string consists of only the letters ‘a’, ‘b’, and ‘c’, and no two consecutive characters in the string are the same. Given two integers n and k, return the kth happy string of length n sorted in lexicographical order, or an empty string if there are fewer than k happy strings of length n.
Given a list of customer orders in a restaurant, return a table where each row represents a table number and the columns represent the number of food items ordered at that table, sorted in lexicographical order.
You are given a string croakOfFrogs, which represents a mix of sounds from multiple frogs croaking the word ‘croak’. Each frog croaks the sequence of letters: ‘c’, ‘r’, ‘o’, ‘a’, ‘k’. Your task is to determine the minimum number of frogs needed to croak all the sounds in the string, while following the correct letter sequence. If the string is not a valid combination of croaks, return -1.
You are given an array cardPoints representing the points of cards arranged in a row. In each step, you can pick the first or the last card from the row. Your goal is to pick exactly k cards and maximize the sum of the points of the cards you select.
You are given a 2D array nums, where each sub-array represents a row in the grid. Your task is to return all the elements of nums in diagonal order, starting from the top-left to bottom-right diagonals, where the sum of the row and column indices is constant.
You are given an integer num and you must apply a set of operations twice to generate two new integers. The goal is to find the maximum difference between the results of these operations.