Binary Search Algorithm

Write a Python Program to perform the binary search.

Program Algorithm:

1.Read the search element

2.Find the middle element in the sorted list

3.Compare the search element with the middle element

i. if both are matching, the print element found

ii. else then check if the search element is smaller or larger than the middle element

4.If the search element is smaller than the middle element, then repeat steps 2 and 3 for the

left sublist of the middle element

5.If the search element is larger than the middle element, then repeat steps 2 and 3 for the

right sublist of the middle element

6.Repeat the process until the search element if found in the list

7.If element is not found, loop terminates 

Program Code:

def bsearch(alist,item):

 first=0

 last=len(alist)-1

 found=False

 while first<=last and not found:

 mid=(first+last)//2

 if alist[mid]==item:

 found=True

 print("element found in position",mid)

 else:

 if item<alist[mid]:

 last=mid-1

else:

 first=mid+mid-1

 return found

a=[]

n=int(input("enter upper limit"))

for i in range(0,n):

 e=int(input("enter the elements"))

 a.append(e)

x=int(input("enter element to search"))

bsearch(a,x)

Program Output:

enter upper limit 6

enter the elements 2

enter the elements 3

enter the elements 5

enter the elements 7

enter the elements 14

enter the elements 25

enter element to search 5

element found in position 2