please find bug in binary search algo

Question

elem = [11,23,8,14,30,9,6,17,22,28,25,15,7,10,19]
arr = sorted(elem)

def binary_search(tgt):
start = 0
end = len(arr)-1

while (start < end):
mid = int((start+end)/2)

if tgt == arr[mid]:
print("At index location ", mid)
break
else:
if tgt < arr[mid]:
end = mid - 1
else:
start = mid + 1
binary_search(30)

#my program not finding some numbers like as: 6,8,10,14,17,22,25,30

Answer 1

Thanks

Answer 2

How i try to find bugs: Print the variables.
add following line after mid=ind((start+end)/2)
print("start",start," mid",mid," end",end," arr",arr[mid])

Answer 3

The problem is the following line:
mid = int(start+end)/2)
If start+end == 15
Then 15/2 = 7.5 and int(7.5) == 7
But the number you are looking for is at arr[8]
One possible way to solve the bug is:
mid= math.ceil((start+end)/2)
and change
start = mid
in the last line of the function
But therefore you would need to have the following line at the beginning:
import math
it doesn't find the first element because of the ceil function though