Main diagonal sum in C: solved exercise

Main diagonal sum in C: solved exercise

If you are looking for main diagonal sum in c: solved exercise, here is a practical, compilable example focused on the reusable idea behind the exercise.

Problem statement

Sum the elements on the main diagonal of a 3x3 matrix.

C solution

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#include <stdio.h>

int main(void) {
    int a[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    int suma = 0;

    for (int i = 0; i < 3; i++) {
        suma += a[i][i];
    }

    printf("%d\n", suma);
    return 0;
}

Expected output

1

15

Common mistakes

  • Not testing edge cases such as small or empty inputs.
  • Not validating indices, pointers, or limits carefully enough.
  • Copying the mechanics without understanding the general pattern.

Practical use

This pattern appears frequently in text handling, input validation, and buffer manipulation.

Guided practice and full book

If you want a complete path with progressive difficulty:

FAQ

Is this exercise useful in practice?

Yes. It is designed to teach a reusable C pattern rather than a one-off toy example.

How should I practice it better?

Change the input data, add edge cases, and rewrite it from scratch without looking at the solution.

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.