Python实现二分法查找（递归与非递归）

#二分查找 递归实现版本
def binary_search(alist, item):

 """
:param alist:
:param item: 查找的元素
:return: True, False
"""
n = len(alist)
if 0 == n:
    return False
mid = n // 2

if alist[mid] == item:
    return True
elif item < alist[mid]:
    return binary_search(alist[:mid], item)
else:
    return binary_search(alist[mid+1:], item)

if name == ‘main’:
testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42]
print(binary_search(testlist, 32))
print(binary_search(testlist, 60))

#二分查找 非递归版本
def binary_search_2(alist, item):

"""
:param alist:
:param item:
:return: True False
"""
start = 0
end = len(alist) - 1
while start <= end:
    mid = (start + end) // 2
    if alist[mid] == item:
        return True
    elif item < alist[mid]:
        end = mid - 1
    else:
        start = mid + 1
return False

if name == ‘main’:
testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42]
print(binary_search_2(testlist, 32))
print(binary_search_2(testlist, 60))