Recursive implementation of python binary search algorithm

高洛峰
Release: 2017-03-02 17:00:04
Original
2428 people have browsed it

The example of this article describes the recursive implementation method of python binary search algorithm. Share it with everyone for your reference, the details are as follows:

Here is a binary search code:

def binarySearch(alist, item):
  first = 0
  last =
len(alist)-1
  found = False
  while first<=last
and not found:
midpoint = (first + last)//2
if alist[midpoint] == item:
   found = True
else:
   if item < alist[midpoint]:
  last = midpoint-1
   else:
  first = midpoint+1
  return found
testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42,]
print(binarySearch(testlist, 3))
print(binarySearch(testlist, 13))
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I like recursion recently is simple and clear, so I changed it to a recursive method:

def binSearch(lst, item):
  mid = len(lst) //2
  found = False
  if lst[mid] ==
item:
 found = True
 return found
  if mid == 0:
#mid等于0就是找到最后一个元素了。
 found = False
 return found
  else:
 if item > lst[mid]: #找后半部分
   #print(lst[mid:])
   return
binSearch(lst[mid:], item)
 else:
   return
binSearch(lst[:mid], item) #找前半部分
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