Euclidean algorithm (GCD) in C: solved exercise

Euclidean algorithm (GCD) in C: solved exercise

This exercise is scheduled for daily publication and follows the standard site structure: statement, solution, and expected output.

Problem statement

Solve the practical case and verify the console output.

C solution

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#include <stdio.h>

int mcd(int a, int b) {
    while (b != 0) {
        int r = a % b;
        a = b;
        b = r;
    }
    return a;
}

int main(void) {
    printf("MCD(48,18) = %d\n", mcd(48, 18));
    return 0;
}

Expected output

1

MCD(48,18) = 6

Common mistakes

  • Not validating standard-function return values.
  • Ignoring edge cases for indices, pointers, or buffers.
  • Skipping example-based test runs before publishing.

Practical use

The GCD with Euclid’s algorithm is used in cryptography, fraction simplification, and solving Diophantine equations.

Guided practice and full book

If you want a complete path with progressive difficulty:

FAQ

Is this exercise useful for C exams and technical interviews?

Yes. It targets patterns that commonly appear in practice assignments, technical interviews, and C programming exams.

Where can I keep practicing with more solved C exercises?

In Programming in C in 100 Solved Exercises and C Exercises. Kindle Unlimited: View on Amazon.

How should I practice this exercise type to improve faster?

Start with small inputs, run edge cases (empty, one item, max capacity), then rewrite the solution from scratch without copying.