/*
    [invert_array.c]
Author : Alessandro Suglia ( alessandro.suglia@gmail.com )
Date : 10/17/2011 15:37

Simple program which shows how to manage a structured
data type like the array. It asks to the user the size of
the array, asks to fill it with n values, and then prints
them to the video, firstly in the inserting order and,
afterthat, inverted.

*/

/* <------------- Header declaration -------------------- > */
#include <stdio.h>
#include <stdlib.h>

/* <-------------- Useful Macros and define --------------> */
#define LEN(x) sizeof(x)/sizeof(int)
#define PRINT_ARRAY(x, n) for ( i = 0; i < n; i++ ) printf("%d)\t%d\n", i+1, x[i])

/* < ------------- Functions' prototype declaration ------> */
void get_array( int [], int );
void invert_array( int [], int );
void swap( int *, int * );

/* <--------------- main() function ----------------------> */
int main()
{
  int *num;
  int n = 0;
  int i  = 0;

  printf("::::::: INVERT ARRAY :::::::::::\n\n");
  printf("What's the array's size?\n");
  scanf("%d", &n);

  if ( n < 0 ) /* Check the size of the array inserted by the user, if it's negative, exit*/
    {
      perror("Nothing to be done with an array with negative size!!\n");
      exit(-1);
    }
  else /* Else, allocates memory for the defined array num */
    {
      num = (int*)malloc( n * sizeof(int));
      if ( !(num) ) /* Check for some errors in the dynamic allocation */
       {
           perror("MALLOC ERROR : FATAL!!\n");
           exit(-1);
       }
      get_array( num, n );
      printf("Value inserted in the array : \n");
      PRINT_ARRAY( num, n );
      printf("\n\n");
      printf("Inverted array values : \n");
      invert_array( num, n );
      PRINT_ARRAY( num, n );

    }
    /* Some sort of stuff that I MUST do in order to make the code portable also with linux */
  #ifdef _WIN32
    system("PAUSE");
  #endif
  return EXIT_SUCCESS;


}
/* It receives the array and its length and then grants to the user to fill it */
void get_array( int a[], int len )
{
  int i;

  printf("Insert %d values : \n", len);
  for ( i = 0; i < len; i++ )
    scanf("%d", &a[i]);

}
/* A kinda of function used to swap the value */
void swap( int *a, int *b )
{
  int temp = *a;
  *a = *b;
  *b = temp;

}
/* Inverts the order of the array's elements */
void invert_array( int a[], int len )
{
  int m = len/2;
  int i;

  for ( i = 0; i < m; i++ )
    swap(&a[i], &a[len-1-i]);
}