Digital Root

Medium Number Theory & Mathematics
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Problem Statement

Write a C program to repeatedly sum the digits of a number until a single-digit number remains (Digital Root).

Input Format

A single integer N.

Output Format

Print the single-digit digital root.

Constraints

0 <= N <= 1000000000

Sample Input

38

Sample Output

2

Explanation

3 + 8 = 11, then 1 + 1 = 2.

Starter Code

#include <stdio.h>

int main() {
    long long n;
    if (scanf("%lld", &n) == 1) {
        // Write your code here
    }
    return 0;
}

Limits

  • Time Limit: 1s
  • Memory Limit: 256MB

Embedded C Programming

Updated: March 15, 2026
Intermediate

Embedded systems rely on efficient low-level programming to interact directly with hardware. In this course, you will learn how to write practical Embedded C programs used in real microcontroller-based systems. Rather than focusing only on theory, this course follows a practice-driven approach. Each lesson includes hands-on coding exercises that simulate real firmware development tasks used