Oscar Dolloway - 5 months ago 21

Python Question

I'm trying to write binary search in python 3.5 but it wont work I'm not sure why.

`def binarySearch(alist, value):`

first = 0

last = len(alist)-1

midpoint = (last//2)

while binarySearch:

if value == alist[midpoint]:

return True and print ("found")

else:

if value < midpoint:

last = midpoint-1

else:

if value > midpoint:

first = midpoint+1

binarySearch([1,2,3,4,5,6,7,8],3)

if I put value as 4 it displays found, if I put anything else nothing happens and its stuck running doing nothing.

Thanks for your help.

Answer Source

User1915011 beat me to my answer. In line with his answer and @wim's comment, I have made the following changes your `binarySearch`

method.

- Changed the loop to use the
`found`

variable - Added an additional assignment to
`midpoint`

inside the loop - Ensure the loop terminates by adding
`first<=last`

Return found after the

`while`

loop to indicate success or failure.`def binarySearch(alist, value): first = 0 last = len(alist)-1 found = False while first<=last and not found: midpoint = (first + last)//2 if value == alist[midpoint]: found = True else: if value < alist[midpoint]: last = midpoint-1 else: if value > midpoint: first = midpoint+1 return found if binarySearch([1,2,3,4,5,6,7,8],3): print "found"`