Binary Search

# Returns index of x in arr if present, else -1 

def binary_search(arr, low, high, x):

    if high >= low: 
        mid = (high + low) // 2

  

        # If element is present at the middle itself 

        if arr[mid] == x: 

            return mid 

  

        # If element is smaller than mid, then it can only 

        # be present in left subarray 

        elif arr[mid] > x: 

            return binary_search(arr, low, mid - 1, x) 

  

        # Else the element can only be present in right subarray 

        else: 

            return binary_search(arr, mid + 1, high, x) 

  

    else: 

        # Element is not present in the array 

        return -1

  

arr = [ 2, 3, 4, 10, 40 ] 

x = 10
result = binary_search(arr, 0, len(arr)-1, x) 
if result != -1: 

    print("Element is present at index", str(result)) 

else: 

    print("Element is not present