You are given an n x n 2D matrix representing an image.
Rotate the image by 90 degrees (clockwise).

Say you have an array for which the $i^{th}$ element is the price of a given stock on day $i$.

Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy one and sell one share of the stock multiple times). However, you may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

通过规范来解决数据冗余以及一些操作异常的情况。在实际生活中，追求最高的范式并不一定是最好的选择，要考虑多方面因素，如查询速度，数据量等等，尽量选择一个满足需求的，合理的结构

目前关系数据库有六种范式：1NF，2NF，3NF，BCNF，4NF，5NF