Python Program to create an OTP by squaring and concatenating the odd digits of a number

Given a number n. The task is to create an OTP by squaring and concatenating the odd digits of the number. Examples:

Input: 4365188
Output: 9256

Input: 123456
Output: 4163

Explanation: In the First example, the integers at odd places are 3, 5, and 8. So we have to return a 4 digit OTP by squaring the digits. The square of the above digits are 9, 25, 65 so the OTP to be returned is the first four digits 9256. Approach: Iterate through the length of the string (number) with the starting index as 1 and taking the step as 2. Initialize an empty string and then concatenate the squares of the odd digit to that string. Finally, return the first four characters of the string as an OTP. Below is the implementation. 

Python3

# python program to generate
# an OTP from the squares of the
# odd digits


def OTP(number):

    # Finding the length
    # of the string
    length = len(number)

    # Declaring an empty string
    # for storing otp
    otp = ''

    # Iterating from index 1
    # with step as 2
    for odd in range(1, length, 2):

        # Concatenating the output
        # to the string
        otp+= str(int(number[odd])**2)

    print(otp[0:4])

# Driver code
number = '4365188'
OTP(number)

Output:

9256

Time Complexity: O(n)

Auxiliary Space: O(n)