Remove duplicates from a sorted array in C: solved exercise

Remove duplicates from a sorted array in C: solved exercise

If you are looking for remove duplicates from a sorted array in c: solved exercise, here is a practical, compilable example focused on the reusable idea behind the exercise.

Problem statement

Compact a sorted array with repeated values so only {1,2,3,4} remains.

C solution

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29

#include <stdio.h>

int eliminar_duplicados(int a[], int n) {
    if (n == 0) {
        return 0;
    }

    int k = 1;
    for (int i = 1; i < n; i++) {
        if (a[i] != a[k - 1]) {
            a[k++] = a[i];
        }
    }
    return k;
}

int main(void) {
    int a[] = {1, 1, 2, 2, 2, 3, 4, 4};
    int n = eliminar_duplicados(a, 8);

    for (int i = 0; i < n; i++) {
        printf("%d", a[i]);
        if (i + 1 < n) {
            printf(" ");
        }
    }
    printf("\n");
    return 0;
}

Expected output

1

1 2 3 4

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

The key idea is to identify a reusable pattern instead of stopping at “it works once”.

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.