reversal_algorithm.c

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

#define ARRAY_LENGTH 6

/* Assuming arrays start at zero*/
int find_opposite(int n, int count){
  /* If arrays start at one, one can use (count+1) - n */
  return count - n;
}

int* reverse_array (int *arr, int length){
  int center = (int) (length / 2);
  int temp;
  for (int head = 0; head < center; head++) {
    temp = arr[head];
    arr[head] = arr[find_opposite(head, length)];
    arr[find_opposite(head, length)] = temp;
  }
  
  return arr;
}

int main (int argc, char *argv[]){
 
 //Initialise and define the new array
 int *a = malloc(sizeof(int) * (ARRAY_LENGTH + 1));
 for (int n = 0; n <= ARRAY_LENGTH; n++)
    a[n] = n;
    
//Print the array
 printf("Original Array:\n");
 
 for (int i = 0; i <= ARRAY_LENGTH; i++)
    printf("%d ", a[i]);

//Reverse and print
 reverse_array(a, ARRAY_LENGTH);

 printf("\nReversed Array:\n");
 
 for (int c = 0; c <= ARRAY_LENGTH; c++)
    printf("%d ", a[c]);

 free(a);
 return 0;
}