Swap in a int array

Question

1.00/5 (1 vote)

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Hi
im going to swap the first int in my arry whit the last.

C#

int[] Tal = new int[10];
Console.WriteLine("10 numbers: ");
for (int i = 0; i < Tal.Length; i++)
{
    Console.Write("number " + (i + 1) + ": ");
    Tal[i] = int.Parse(Console.ReadLine());
}
 Arra c = new Array();
 c.FirstLast(Tal)

C#

  public void FirstLast(int[] arr)
{
    foreach (int t in arr)
    {
        int temp = arr[0];
        arr[0] = arr[9];
        arr[9] = temp;
        Console.WriteLine(t);
    }

when i type in 1,2,3,4,5,6,7,8,9,10 and then it show 1,2,3,4,5,6,7,8,9,1
i want it to be 10,2,3,4,5,6,7,8,9,1. I know i replace the first whit the last but way dos it not replace the first one to whit the last.

sorry for the bad english. I hope someone will understand it

Posted 10-Mar-13 7:16am

zxcvasdf1

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3 solutions

Solution 3

C#

 int j = 9;
int[] arr = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int[] arr2 = new int[10];
for (int i = 0; i < arr.Length; i++)
{
   arr2[j--] = arr[i];
   Console.WriteLine(arr2[i]);
}
for (int i = 0; i < arr2.Length; i++)
{
    Console.WriteLine(arr2[i]);

}
Console.ReadKey();

Posted 10-Mar-13 8:22am

deepak Singh m

Updated 10-Mar-13 8:24am

v2

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Thomas Daniels · Accepted Answer · 2013-03-10T07:28:00

Solution 1

Hi,

Try this:

C#

public void SwapFirstAndLast(ref int[] array)
{
     int temp = array[0];
     int posOfLast = array.Length - 1;
     array[0] = array[posOfLast];
     array[posOfLast] = temp;
}

How to use this swap method:

C#

SwapFirstAndLast(ref intArray); // change intArray into the name of your array

More about the ref keyword: http://msdn.microsoft.com/en-us/library/14akc2c7.aspx[^]

Hope this helps.

Posted 10-Mar-13 7:28am

Thomas Daniels

Comments

zxcvasdf1 10-Mar-13 13:42pm

thx for this i will try this is always good to learn something new

Thomas Daniels 10-Mar-13 13:43pm

You're welcome!

Sharp Robin · Accepted Answer · 2013-03-10T07:35:00

You should probably take the swapping code out from the foreach loop:

C#

public void FirstLast(int[] arr)
{
    int temp = arr[0];
    arr[0] = arr[9];
    arr[9] = temp;

    foreach (int t in arr)
    {
        Console.WriteLine(t);
    }
}

And, yes definitely use ref in function call that swaps the values so that you can show your result in console, window or what do I know maybe return as value in another function.

Happy coding.