Can someone help me? I need to write a "reverse" function that reads the inverse of the vector using pointers. Example: typed 123, printed 321

Question

#include <stdio.h>
#include <stdlib.h>

void inverte (int *original, unsigned int qtd, int *invertido){
    
}

int main()
{
    int qtd;
    int v[100];
    int *n;
    qtd = 0;
    for (int i = 0; i < 100; i++)
    {
        printf("Digite um valor (-1 para parar): ");
        scanf("%d", &v[i]);
        if (v[i] == -1)
            break;
        qtd++;
    }

    inverte (v, qtd, &n);

    printf("Valores na ordem inversa\n");
    for (int i = 0; i < qtd; i++)
        printf("%d ", n[i]);

    return 0;
}

Answer 1

With this implementation, the function returns the inverted vector:

#include <stdio.h>
#include <stdlib.h>

int *inverter(const int *vetor, size_t tamanho);

int main() {
    const int maximo = 10;
    int tamanho = 10;
    int vetor[maximo];
    int *inverso;

    // Inicializa o vetor: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
    for (int i = 0; i < maximo; ++i) {
        vetor[i] = i + 1;
    }

    inverso = inverter(vetor, tamanho);

    printf("[");

    for (int i = 0; i < tamanho; ++i) {
        printf("%d", inverso[i]);

        if (i + 1 < tamanho) {
            printf(", ");
        }
    }

    printf("] \n");
    return EXIT_SUCCESS;
}

int *inverter(const int *vetor, size_t tamanho) {
    int *resultado = (int *) malloc(tamanho * sizeof(int));

    for (int i = 0, j = (int) tamanho - 1; i < tamanho; ++i, --j) {
        resultado[i] = vetor[j];
    }

    return resultado;
}

If you don’t need to return an inverted vector, just rotate a loop backwards (starting with the size and decreasing to zero) in the original vector.