循环
def binary_search(alist, item):
first = 0
last = len(alist)-1
while first<=last:
midpoint = (first + last)/2
if alist[midpoint] == item:
return True
elif item < alist[midpoint]:
last = midpoint-1
else:
first = midpoint+1
return False
testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42,]
print(binary_search(testlist, 3))
print(binary_search(testlist, 13))
递归
def binary_search(alist, item):
if len(alist) == 0:
return False
else:
midpoint = len(alist)//2
if alist[midpoint]==item:
return True
else:
if item<alist[midpoint]:
return binary_search(alist[:midpoint],item)
else:
return binary_search(alist[midpoint+1:],item)
testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42,]
print(binary_search(testlist, 3))
print(binary_search(testlist, 13))