Selection sort in C: solved exercise step by step

Selection sort in C: solved exercise step by step

This exercise is scheduled for daily publication and follows the same didactic structure used across the site: clear statement, compilable code, and expected output.

Problem statement

Implement a practical example of the topic and validate the output in the console.

C solution

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#include <stdio.h>

void selection_sort(int a[], int n) {
    for (int i = 0; i < n - 1; i++) {
        int min = i;
        for (int j = i + 1; j < n; j++) {
            if (a[j] < a[min]) min = j;
        }
        int tmp = a[i];
        a[i] = a[min];
        a[min] = tmp;
    }
}

int main(void) {
    int v[] = {6, 2, 9, 1, 5};
    int n = (int)(sizeof(v) / sizeof(v[0]));
    selection_sort(v, n);
    for (int i = 0; i < n; i++) printf("%d ", v[i]);
    printf("\n");
    return 0;
}

Expected output

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1 2 5 6 9

Common mistakes

  • Not validating input and standard-library return values.
  • Ignoring edge cases (buffers, limits, null pointers).
  • Skipping basic compile/run verification.

Practical use

Selection sort is used when writes are expensive, as it performs the minimum number of swaps possible.

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.