0258.Add Digits

Link: 258. Add Digits - Easy
Track: Amazon Tag

Question

Restate

Edge Case

• num = 0, return 0

---

Method 1 - simulation
Method 2 - math

Method 1 - simulation

Approach

(discussed at lease two approach?)

Complexity

• Time Complexity: O(d)
• Space Complexity: O(1)

Code

class Solution:
    def addDigits(self, num: int) -> int:
        while num >= 10:
            total = 0
            while num > 0:
                total += num % 10
                num //= 10
            num = total
        
        return num

Method 2 - Math

Complexity

• Time Complexity: O(1)
• Space Complexity: O(1)

Code

class Solution:
    def addDigits(self, num: int) -> int:
        if num == 0:
            return 0
        return 1 + (num - 1) % 9

---

History

• Feb-19-2026 Peeked