Write a python program to perform Binary Search

Binary Search

Given a sorted array A and an element to search E, find the index of the element using the binary search algorithm. If the element is not found in the array return -1. 

 

 

Input:

    10 
    2 4 5 6 8 12 15 18 30 54
    8 

• The first line represents the size of an array. 

• The second line represents array elements. 

• The third line represents the element to search. 

    4 

 

    where, 

 

Output:

 

The given array contains the element 8 at index 4 (index starts from 0).

Code:- 

Method 1:- 

def solution(arr,x):

    l,m,h=0,len(arr)-1,0

    while l<=h:

        m=(h+l)//2

        if arr[m] < x:

            l=m+1

        elif arr[m] >x :

            h=m-1

        else:

            return m

    return -1

arr= []

n=int(input())

  # use for loop to fill numbers list with elements

for i in range(n):

    s=int(input())

    arr.append(s)

print(arr)

x=int(input())

re=solution(arr,x)

if re!=-1:

    print(str(re))

else:

    print(-1)

Method 2:-

def solution(arr,x):

    l=0

    h=len(arr)-1

    m=int((h+l)//2)

    while l<=h:

        m=int((h+l)//2)

        if arr[m]==x:

            return m

        if arr[m] < x:

            l=m+1

        if arr[m] >x :

            h=m-1

    return -1

arr= []

N=int(input())

L=[]

n=0

for e in input().split():

    if(n<N):

        arr.append(int (e))

        n+=1

x  = int(input())

print(solution(arr,x),end='')