Sum of Digits of a Number

📌 Definition:

📖 Detailed Explanation:

Repeatedly take the last digit with % 10, add it to a running sum, and drop it with integer division by 10 until the number is zero. O(number of digits). A recursive variant sums digit + sumDigits(n / 10).

💻 Solutions:

• Java
• JavaScript
• Python

public static int sumDigits(int n) {
    n = Math.abs(n);
    int sum = 0;
    while (n != 0) { sum += n % 10; n /= 10; }
    return sum;
}

function sumDigits(n) {
  n = Math.abs(n);
  let sum = 0;
  while (n !== 0) { sum += n % 10; n = Math.floor(n / 10); }
  return sum;
}

def sum_digits(n):
    return sum(int(d) for d in str(abs(n)))

🔑 Key Points:

• Extract digits with %10 and /10
• Loop until the number is zero
• Take absolute value for negatives
• Recursive form is a common follow-up

🌍 Real-World Example: