二分法
掐头结尾取中间
查找效率非常的高
# 二分法查找主要的作用就是查找元素
# lst = [1,3,5,7,12,36,68,79] # 数据集 百万级数据
# nl = int(input("请输入你要查找的数字:"))
# left = 0
# right = len(lst)-1
# while left <= right:
# mid = (left+right)//2
# if nl > lst[mid]:
# left = mid + 1
# elif nl < lst[mid]:
# right = mid - 1
# else:
# print("存在")
# break
# else:
# print("不存在")
# 递归
# def func(n, lst, left, right):
# mid = (left+right) // 2
# if left <= right:
# 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)
# else:
# print("存在")
# return mid
# else:
# print("不存在")
# return -1
# n = int(input("请输入你要查找的数:"))
# lst = [1,3,5,7,12,36,68,79]
# func(n, lst, 0, len(lst)-1)
