python之二分法查找

二分法查找主要的作用就是查找元素

规则. 掐头结尾取中间, 必须是有序列

# 二分法查找 (需要你明白和掌握)
# lst = [1,3,5,7,12,36,68,79]
# n = int(input("请输入一个数"))
#
# left = 0
# right = len(lst) - 1
#
# while left <= right:
#     mid = (left + right)//2
#     if n > lst[mid]:
#         left = mid + 1
#     elif n < lst[mid]:
#         right = mid - 1
#     else:
#         print("存在")
#         break
#
# else:
#     print("不存在")

　　

# 递归二 (需要你明白和掌握)
# def func(n, lst, left, right): # 递归找到什么是可以变的. 什么是不可以变的
#     if left <= right:
#         mid = (left + right) // 2
#         if n > lst[mid]:
#             left = mid + 1
#             return func(n, lst, left, right)
#         elif n < lst[mid]:
#             right = mid - 1
#             return func(n, lst, left, right) # 递归如果有返回值. 所有调用递归的地方必须写return
#         else:
#             print("找到了")
#             return mid  # 难点
#     else:
#         print("找不到")
#         return -1
#
# n = int(input("请输入你要查找的数:"))
# lst = [1,3,55,98,37,41,2,5,1,4]
# ret = func(n, lst, 0, len(lst)-1) # 78
# print(ret)

　　

#  最快的查找
lst = [1,3,55,98,37,41,2,5,1,4]
new_lst = []
for i in range(99):
    new_lst.append(0)
for i in lst:    # 1,3,55,98
    new_lst[i] = 1
print(new_lst)
i = int(input('请输入你要找的数据'))
if new_lst[i] == 0: # 1次
    print("不存在")
else:
    print("存在")