python 二分查找

1. 二分查找是有条件的，首先是有序，其次因为二分查找操作的是下标，所以要求是顺序表
2. 最优时间复杂度：O(1)
3. 最坏时间复杂度：O(logn)

def binary_chop(alist, data):
“”"
递归解决二分查找
:param alist:
:return:
“”"
n = len(alist)
if n < 1:
return False
mid = n // 2
if alist[mid] > data:
return binary_chop(alist[0:mid], data)
elif alist[mid] < data:
return binary_chop(alist[mid+1:], data)
else:
return True

def binary_chop(alist, data):
“”"
非递归解决二分查找
:param alist:
:return:
“”"
n = len(alist)
first = 0
last = n - 1
while first <= last:
mid = (last + first) // 2
if alist[mid] > data:
last = mid - 1
elif alist[mid] < data:
first = mid + 1
else:
return True
return False

if name == ‘main’:
lis = [2,4, 5, 12, 14, 23,56]
a=binary_chop(lis, 2)
print(a)