807. Max Increase to Keep City SkylineIn a 2 dimensional array grid, each value grid[i][j] represents the height of a bu

804. Unique Morse Code WordsInternational Morse Code defines a standard encoding where each letter is mapped to a series

771. Jewels and StonesYou’re given strings Jrepresenting the types of stones that are jewels, and S representing the sto

709. To Lower CaseImplement function ToLowerCase() that has a string parameter str, and returns the same string in lower

657. Robot Return to OriginThere is a robot starting at position (0, 0), the origin, on a 2D plane. Given a sequence of

627. Swap SalarySQL架构 create table if not exists salary(id int, name varchar(100), sex char(1), salary int) Truncate tab

620. Not Boring MoviesSQL架构 Create table If Not Exists cinema (id int, movie varchar(255), description varchar(255), rat

595. Big CountriesSQL架构 Create table If Not Exists World (name varchar(255), continent varchar(255), area int, populatio

561. Array Partition IGiven an array of 2n integers, your task is to group these integers into n pairs of integer, say (

509. Fibonacci NumberThe Fibonacci numbers, commonly denoted F(n) form a sequence, called the Fibonacci sequence, such t

476. Number ComplementGiven a positive integer, output its complement number. The complement strategy is to flip the bit

461. Hamming DistanceThe Hamming distance between two integers is the number of positions at which the corresponding bit