# Python Program for Binary Search

In this article, we will learn about the solution and approach to solve the given problem statement.

Problem statement − We will be given a sorted list and we need to find an element with the help of a binary search.

## Algorithm

• Compare x with the middle element.

• If x matches with the middle element, we return the mid index.

• Else If x is greater than the mid element, then x can only lie in right half subarray after the mid element. So we recur for the right half.

• Else (x is smaller) recur for the left half

## Example

def binarySearchAppr (arr, start, end, x):
# check condition
if end >= start:
mid = start + (end- start)//2
# If element is present at the middle
if arr[mid] == x:
return mid
# If element is smaller than mid
elif arr[mid] > x:
return binarySearchAppr(arr, start, mid-1, x)
# Else the element greator than mid
else:
return binarySearchAppr(arr, mid+1, end, x)
else:
return -1
arr = sorted(['t','u','t','o','r','i','a','l'])
x ='r'
result = binarySearchAppr(arr, 0, len(arr)-1, x)
if result != -1:
print ("Element is present at index "+str(result))
else:
print ("Element is not present in array")

## Example

Live Demo

def binarySearchAppr (arr, start, end, x):
# check condition
if end >= start:
mid = start + (end- start)//2
# If element is present at the middle
if arr[mid] == x:
return mid
# If element is smaller than mid
elif arr[mid] > x:
return binarySearchAppr(arr, start, mid-1, x)
# Else the element greator than mid
else:
return binarySearchAppr(arr, mid+1, end, x)
else:
return -1
arr = sorted(['t','u','t','o','r','i','a','l'])
x ='r'
result = binarySearchAppr(arr, 0, len(arr)-1, x)
if result != -1:
print ("Element is present at index "+str(result))
else:
print ("Element is not present in array")
Element is present at index 4