遞歸(難點)
自己調用自己
遞歸的入口
遞歸的出口: return
遞歸的循環條件：動
循環樹形結構

# 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視頻",0)

二分法查找
核心思想: 掐頭結尾取中間.
前提條件: 有序.

lst = [1, 8, 16, 32, 55, 78, 89, 1, 5, 4, 1, 3, 4, 8, 9, 5]
# #二分法查找數字首先要排序
lst = sorted(lst)
# print(lst)
#[1, 1, 1, 3, 4, 4, 5, 5, 8, 8, 9, 16, 32, 55, 78, 89]
n = int(input("請輸入一個數字: "))
left = 0
right = len(lst)-1
while left <= right:
    mid = (left + right) // 2  #索引只能是整數
    if n > lst[mid]:
        left = mid+1
    elif n < lst[mid]:
        right = mid - 1
    else:
        print("剛剛好,所在位置%s" % mid)
        break
else:
    print("查找的數不存在")
#函數第一套方案
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("剛剛好,所在位置%s"% mid)
            return True
    else:
        return False
print(func(3, lst))
#函數第二套方案
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)
#關鍵字參數
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)

遞歸和二分法