Cassidoo IQofW 2020-01-13

palindrome-sum.py

# cassidoo Interview Question of the Week: January 13, 2020
# Given a number n, find the sum of all n-digit palindromes.

# Example:
# > nPalindromes(2)
# > 495 // 11 + 22 + 33 + 44 + 55 + 66 + 77 + 88 + 99

def nPalindromes(length):
    sum = 0
    if length == 0:
        return sum
    elif length == 1:
        for digit in range(1,10):
            sum += digit
        return sum
    elif length == 2:
        for digit in range(1,10):
            sum += (digit * 10) + digit
        return sum
    else:
        nP1 = nPalindromes(1)
        sum  = nP1 * (10 ** (length - 1)) * (10 ** int(length / 2)) 
        sum += nPalindromes(length - 2) * 90
        sum += nP1 * (10 ** (int(length / 2)))
        return sum

for digit in range(2,10):
    print("sum of " + str(digit) + "-digit palindrome numbers = " + str(nPalindromes(digit)))