说明：  经典算法可以说是每个程序员都必须得掌握的了，花了一天的时间把代码实现且整理了一下，为了方便大家学习，每种算法会有简单的算法思想描述
(It can be said that every programmer must master the classic algorithm. It took a day to implement and sort out the code. In order to facilitate everyone to learn, each algorithm will have a simple description of the algorithm idea)