What is the most efficient way to execute this code?

Question

My teacher asked us to make a program in the most efficient way possible and to use a switch case for this.

The program asks the user for input, and depending on what the user inputs, the program will have to follow a set of instructions.

If the input is "A" or "a", the array has to be sorted from A to Z.

If the input is "Z" or "z", the array has to be sorted from Z to A.

If the input is "R" or "r", the array has to be reversed.

The array is a string[].

So I'm wondering if it's more effecient to use

switch (choice.ToLower())
{
    case "a":
        Array.Sort(array);
        break;
    case "z":
        Array.Sort(array);
        Array.Reverse(array);
        break;
    case "r":
        Array.Reverse(array);
        break;
}

or

 if (choice.ToLower() == "a" || choice.ToLower() == "z")
 {
     Array.Sort(array);
 }

 if (choice.ToLower() == "r" || choice.ToLower() == "z")
 {
     Array.Reverse(array);
 }

and also if this code can be optimised even further.

So, is the most efficient way to use a switch case, or the if structure as seen above and explain why?

I'm just curious since I always try to optimise all my code to full extent.

Answer 1

Well, you can check it by yourself :

class Program
{
    static void MyMethod1(int[] array, string choice)
    {            
        switch (choice.ToLower())
        {
            case "a":
                Array.Sort(array);
                break;
            case "z":
                Array.Sort(array);
                Array.Reverse(array);
                break;
            case "r":
                Array.Reverse(array);
                break;
        }
    }

    static void MyMethod2(int[] array, string choice)
    {            
        if (choice.ToLower() == "a" || choice.ToLower() == "z")
        {
            Array.Sort(array);
        }

        if (choice.ToLower() == "r" || choice.ToLower() == "z")
        {
            Array.Reverse(array);
        }
    }

    static int[][] CreateRandomArrays(int num, int length)
    {
        Random rand = new Random();
        int[][] arrays = new int[num][];

        for (int i = 0; i < arrays.Length; i++)
        {
            arrays[i] = new int[length];
            for (int i2 = 0; i2 < length; i2++)
                arrays[i][i2] = rand.Next();
        }

        return arrays;
    }

    static void Main(string[] args)
    {
        int[][] test1 = CreateRandomArrays(50, 200000);
        int[][] test2 = CreateRandomArrays(50, 200000);

        Stopwatch s = new Stopwatch();

        s.Start();

        for (int i = 0; i < test1.Length; i++) MyMethod1(test1[i], "z");

        s.Stop();
        Console.WriteLine(s.ElapsedMilliseconds);

        s.Restart();            

        for (int i = 0; i < test2.Length; i++) MyMethod2(test2[i], "z");

        s.Stop();

        Console.WriteLine(s.ElapsedMilliseconds);
    }
}

As you can see result is almost identical :

1010 ms    vs    1008 ms