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.
1public class AddDigitsIterative {
2 public static int addDigits(int num) {
3 while (num >= 10) {
4 int sum = 0;
5 while (num > 0) {
6 sum += num % 10;
7 num /= 10;
8 }
9 num = sum;
10 }
11 return num;
12 }
13
14 public static void main(String[] args) {
15 int num = 38;
16 System.out.println(addDigits(num));
17 }
18}In Java, the approach involves looping through the digits, summing them, and using the same integer operations to yield a reduced number until it is a single digit.
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.
1public class
Java uses similar logic, ensuring that the mathematical reduction via modulo provides the result in constant time.