Question

Write a method swaparrayends() that swaps the first and last elements of its array parameter. ex: sortarray = {10, 20, 30, 40} becomes {40, 20, 30, 10}. the array's size may differ from 4.

Answer 1

In the C programming language, you can't determine the array size from the parameter, so you have to pass it in as an extra parameter. The solution could be:

#include <stdio.h>

void swaparrayends(int arr[], int nrElements)
{
int temp = arr[0];
arr[0] = arr[nrElements - 1];
arr[nrElements - 1] = temp;
}


void main()
{
int i;
int myArray[] = { 1,2,3,4,5 };
int nrElements = sizeof(myArray) / sizeof(myArray[0]);
swaparrayends(myArray, nrElements);

for (i = 0; i < nrElements; i++)
{
printf("%d ", myArray[i]);
}

getchar();
}

In higher languages like C# it becomes much simpler:

        static void Main(string[] args)
        {
            int[] myArray = {1, 2, 3, 4, 5};
            swaparrayends(myArray);
            foreach (var el in myArray)
            {
                Console.Write(el + " ");
            }

            Console.ReadLine();
        }

        static void swaparrayends(int[] arr)
        {
            int temp = arr[0];
            arr[0] = arr.Last();
            arr[arr.Length - 1] = temp;
        }