What is the optimal time complexity of solving Sum of digits of a number?

The optimized solution achieves a time complexity of O(n) by using sorting, mathematical shortcuts, or hash table lookups.

What is the auxiliary space complexity for Sum of digits of a number?

The space complexity is O(1) since we only use a minimal/constant amount of extra memory for tracking variables (or auxiliary space if dynamic structures are allocated).

What are the typical edge cases we must handle in Sum of digits of a number?

Key edge cases include empty collections, negative or large bounds causing integer overflow, arrays with only one element, or inputs where target criteria are not met.

How can we optimize the brute force approach for Sum of digits of a number?

Brute force methods often inspect all possible combinations. We optimize this by sorting the input list to enable binary search, or tracking processed items in a set to avoid redundant nested loop lookups.

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Python BasicsEasy

Sum of digits of a number

Learn how to solve the 'Sum of digits of a number' problem. This detailed resource details brute force and optimized approaches.

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Problem Statement

Easy

Write a function sum_of_digits(n) that takes a non-negative integer n and returns the sum of its digits. For example, the digits of 123 are 1, 2, and 3, and their sum is 6.

Constraints

•0 <= n <= 10^9

Examples

Example 1

Input

n = 123

Output

Explanation

1 + 2 + 3 = 6.

Example 2

Input

n = 9999

Output

Explanation

9 + 9 + 9 + 9 = 36.

Example 3

Input

n = 0

Output

Explanation

The only digit is 0, so the sum is 0.

Need a Hint?

Use simple arithmetic operators (like modulo `%`, division `//`), conditional checks, or loops to inspect number properties.

Edge Cases to Watch

Empty list or null input variables
Single item lists/arrays
Extremely large input bounds causing integer or stack overflow

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