Sponsored
Sponsored
The iterative approach involves summing the digits of the number repeatedly until the sum becomes a single-digit number. This is a straightforward approach and uses basic loops to repeatedly process the digits of the number.
1def add_digits(num):
2 while num >= 10:
3 sum = 0
4 while num > 0:
5 sum += num % 10
6 num //= 10
7 num = sum
8 return num
9
10print(add_digits(38))Python's implementation uses loops to compute the sum of the digits repeatedly until a single-digit number is obtained.
The mathematical approach leverages a known number theory result related to digit root which can be deduced using modulo 9 arithmetic. The result for the repeated digit sum is equivalent to the number modulo 9, except that when the number is zero it should remain zero.
1#include
This C solution uses modulo 9 to calculate the digit root. This gives us a constant time solution which is highly efficient.