By giving you an array of points and an integer angle representing the angle, your position is location, and using a certain rotation movement, returns the maximum number of points you can see; Calculate how many days have passed between two dates; Given a string s, please find the length of the longest substring that does not contain duplicate characters; Give you a string word, and return the total number of vowels in all substrings of word. These are always for you to learn more simple knowledge points, to lay a more difficult foundation in the future, to cope with the digital life ahead, and to work hard.