#include <stdio.h>
#include <assert.h>
void swap(int *a ,int *b)
{
    int tmp = *a;
    *a = *b;
    *b = tmp;
}
void show(int arr[], int len)
{
    assert(arr);
    assert(len > 0);
    int i = 0;
    for (; i < len; i++){
        printf("%d ", arr[i]);
    }
    printf("\n");
}
 
void reverse(int arr[], int len)
{
    assert(arr);
    assert(len > 0);
    int *p = arr;
    int *q = arr + len - 1;
    while (p < q){
        swap(p, q);
        p++, q--;
    }
}
 
int main()
{
    int arr[] = {1,2,3,4,5,6,7,8};
    int len = sizeof(arr) / sizeof(arr[0]);
    show(arr, len);    
    reverse(arr, len);
    show(arr, len);
    return 0;
}