递归(难点)

        自己调用自己

        递归的入口

        递归的出口: return

        递归的循环条件：动

        循环树形结构

# import os # def func(file_path,ceng): #     lst = os.listdir(file_path) #     for file in lst: #         full_path = os.path.join(file_path, file) #         if os.path.isdir(full_path): #             print("\t"*ceng, file) #             func(full_path, ceng+1) #         else: #             print("\t"*ceng, file) #     else: #         return # func("F:\python视频",0)

   二分法查找

        核心思想: 掐头结尾取中间.

        前提条件: 有序.

lst = [1, 8, 16, 32, 55, 78, 89, 1, 5, 4, 1, 3, 4, 8, 9, 5] # #二分法查找数字首先要排序 lst = sorted(lst) # print(lst) #[1, 1, 1, 3, 4, 4, 5, 5, 8, 8, 9, 16, 32, 55, 78, 89] n = int(input("请输入一个数字: ")) left = 0 right = len(lst)-1 while left <= right:     mid = (left + right) // 2  #索引只能是整数     if n > lst[mid]:         left = mid+1     elif n < lst[mid]:         right = mid - 1     else:         print("刚刚好,所在位置%s" % mid)         break else:     print("查找的数不存在") #函数第一套方案 def func(n,lst):     left = 0     right = len(lst)-1     if left <= right:         mid = (left+right)//2         if n > lst[mid]:             new_list = lst[mid+1:]             return func(n, new_list)#####################         elif n < lst[mid]:             new_list =lst[: mid]             return func(n, new_list)#####################         else:             print("刚刚好,所在位置%s"% mid)             return True     else:         return False print(func(3, lst)) #函数第二套方案 def func(n, lst, left, right):     if left <= right:         mid = (left+right)//2         if n > lst[mid]:             left = mid + 1         elif n < lst[mid]:             right = mid - 1         else:             return True         return func(n, lst, left, right)     else:         return False ret = func(89,lst,0,len(lst)-1) print(ret) #关键字参数 def func(n, lst, left=0, right=None):     if right == None:         right = len(lst)-1     if left <= right:         mid = (left+right)//2         if n > lst[mid]:             left = mid + 1         elif n < lst[mid]:             right = mid - 1         else:             return True         return func(n, lst, left, right)     else:         return False ret = func(90,lst) print(ret)