双向循环链表，函数初始化，函数功能：增加节点，删除节点，查找节点。-Two-way circular linked list function initializes the function: add nodes, delete nodes, find nodes.

Quicksort is a divide and conquer algorithm. Quicksort first divides a large list into two smaller sub-lists: the low elements and the high elements. Quicksort can then recursively sort the sub-lists. The steps are: Pick an element, called a pivo