Reverse elements in an array

Question

I setup an array and i would like to create a method that will return an array with the elements in reverse. e.g. if there are 10 slots then array1[9] = 6 so

Answer 1

You should be able to use the extension method Reverse

int[] arr = { 43, 22, 1, 44, 90, 38, 55, 32, 31, 9 };
Console.WriteLine("Before");
PrintArray(arr);
Console.WriteLine("After");
PrintArray(arr.Reverse().ToArray());

Or if you don't mind modifing the original sequence you can use Array.Reverse

int[] arr = { 43, 22, 1, 44, 90, 38, 55, 32, 31, 9 };
Console.WriteLine("Before");
PrintArray(arr);
Array.Reverse(arr);
Console.WriteLine("After");
PrintArray(arr);

Answer 2

You can reverse an array by swapping elements from both ends of the array till you reach the middle.

for(int start = 0, end = arr.Length - 1; start < arr.Length/2; start++, end--)
{
     swap(arr[start], arr[end]);
}

Answer 3

Create a new array that has the same length as the old array and reverse is done like this

index -> new index  
  0   -> length - 1  
  1   -> length - 1 - 1  
  2   -> length - 1 - 2  
..  
  i   -> length - 1 - i

so this translates to this code

int[] myVariable = new int[] { 1, 2, 3, 4, 5 };
int[] reversedVariable =  new int[myVariable.Length]();
for (int i = 0; i < myVariable.Length ; i++)
{
    reversedVariable[myVariable.Length - 1 - i] = myVariable[i];
}
return reversedVariable;

Answer 4

       int a;
        Console.WriteLine("Enter the array length");
        a=int.Parse(Console.ReadLine());
        Console.WriteLine("enter the array element");
        int[] sau = new int[a];
        for (int i = 0; i < a; i++)
        {
            sau[i] = int.Parse(Console.ReadLine());
        }
        for (int i =a.Length-1 ; i < 0;i--)
        {
            Console.WriteLine(sau[i]);
        }
            Console.ReadLine();
    }
}

}

Answer 5

 public class MyList<T> : IEnumerable<T>
{
    private T[] arr;

    public int Count
    {
        get { return arr.Length; }
    }            
public void Reverse()
    {
        T[] newArr = arr;
        arr = new T[Count];
        int number = Count - 1;
        for (int i = 0; i < Count; i++)
        {
            arr[i] = newArr[number];
            number--;
        }
    }
}

Answer 6

You can use Array.Reverse

Example from above line

public static void Main()  {

  // Creates and initializes a new Array.
  Array myArray=Array.CreateInstance( typeof(String), 9 );
  myArray.SetValue( "The", 0 );
  myArray.SetValue( "quick", 1 );
  myArray.SetValue( "brown", 2 );
  myArray.SetValue( "fox", 3 );
  myArray.SetValue( "jumps", 4 );
  myArray.SetValue( "over", 5 );
  myArray.SetValue( "the", 6 );
  myArray.SetValue( "lazy", 7 );
  myArray.SetValue( "dog", 8 );

  // Displays the values of the Array.
  Console.WriteLine( "The Array initially contains the following values:" );
  PrintIndexAndValues( myArray );

  // Reverses the sort of the values of the Array.
  Array.Reverse( myArray );

  // Displays the values of the Array.
  Console.WriteLine( "After reversing:" );
  PrintIndexAndValues( myArray );
}


public static void PrintIndexAndValues( Array myArray )  {
  for ( int i = myArray.GetLowerBound(0); i <= myArray.GetUpperBound(0); i++ )
     Console.WriteLine( "\t[{0}]:\t{1}", i, myArray.GetValue( i ) );
}