aux = vetor[i+8];
     vetor[i+8] = vetor[i];
     vetor[i] = aux;

#include <stdio.h>
int main() {

   int arr[5] = {1,2,3,4,5};
   int num = sizeof(arr) / sizeof(int);
   int vetor[num];
   int i, count;

   count = 0;
   for (i = num-1; i >= 0; i--) {
      vetor[count] = arr[i];
      count ++;
   }

   for (i = 0; i < num; i++) {
      printf("%d n", vetor[i]);
   }

   return (0);
}

#include <vector>
#include <algorithm>

void main() {
  std::vector<int> vetor_xpto;
  //quando popular pode usar...
  std::reverse(vetor_xpto.begin(), vetor_xpto.end());
}