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Recursive implementation of python binary search algorithm

高洛峰
高洛峰Original
2017-03-02 17:00:042446browse

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))

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

The test passed.


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