Given a positive integer k, find the length of the smallest positive integer n such that n is divisible by k, and n consists only of the digit 1. If no such number exists, return -1. Note that n might not fit into a 64-bit signed integer.
Given an array of integers, you need to return the length of the longest subsequence where the difference between consecutive elements is constant. A subsequence is derived by deleting some elements without changing the order of the remaining elements. A sequence is considered arithmetic if the difference between consecutive elements remains the same.
You are given an array of words, where each word consists of lowercase English letters. A wordA is considered a predecessor of wordB if you can insert exactly one letter anywhere in wordA without changing the order of the other characters to make it equal to wordB. A word chain is a sequence of words such that each word is a predecessor of the next one. Your task is to find the length of the longest word chain that can be formed from the given list of words.
You are given an array of barcodes where each element represents a barcode. Your task is to rearrange the barcodes such that no two adjacent barcodes are the same. It is guaranteed that a solution exists, and you may return any valid rearrangement.
You are given an m x n binary matrix. You can choose any number of columns in the matrix and flip every cell in that column (i.e., change the value of the cell from 0 to 1 or vice versa). Your task is to find the maximum number of rows that can be made equal after performing a number of column flips.
You are given a string tiles containing uppercase English letters, where each letter represents a tile. You need to return the number of distinct non-empty sequences of letters that can be formed by selecting tiles from the string. A sequence can be formed by selecting tiles in any order and any number of times, but no tile can be used more than once in a sequence.