my shuffle string[] not working?

Question

I tried to write a shuffle string array algo but I get a null reference error.. I can't figure out why..

public static string[] arrRandomized;
public static string[] ShuffleWords(string[] Words)
{
    Random generator = new Random();
    for (int i=0;i < Words.Length; i++) {
        int pos = generator.Next(Words.Length);
        Console.WriteLine(Words[pos]); // I SEE RANDOM ITEM
        Console.Read(); // NULL REFERENCE ERROR AFTER THIS
        if (Words[pos] != null)
        {
            arrRandomized[i] = Words[pos];
            //remove item at pos so I get no duplicates
            Words[pos] = null;
        }
    }

I don't want to use ArrayList, i have my reasons but thats off topic I just want to know how come this isn't working :/ thanks

Changing a collection (or array) while iterating over it is inadvisable. — Oded
– Oded, Commented Nov 10, 2012 at 18:23

Paolo Tedesco · Accepted Answer · 2012-11-10 18:38:53Z

3

I think you should initialize arrRandomized:

arrRandomized = new string[Words.Length];

answered Nov 10, 2012 at 18:38

Paolo Tedesco

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Comments

Brad · Accepted Answer · 2012-11-10 18:40:22Z

0

Your arrRandomized is never intialized. I would also recommend that you return an array rather then use a static reference because the subsequent calls to the method will change all references to the arrRandomized.

public static string[] ShuffleWords(string[] Words)
{    
    string[] arrRandomized = new string[Words.Length];
    Random generator = new Random();
    for (int i=0;i < Words.Length; i++) 
    {
        int pos = generator.Next(Words.Length);
        Console.WriteLine(Words[pos]); // I SEE RANDOM ITEM
        Console.Read(); // NULL REFERENCE ERROR AFTER THIS
        if (Words[pos] != null)
        {
            arrRandomized[i] = Words[pos];
            //remove item at pos so I get no duplicates
            Words[pos] = null;
        }
    }
    return arrRandomized;
}

answered Nov 10, 2012 at 18:40

Brad

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1 Comment

ace007 Over a year ago

got ridd of the error, but now the return array only has 2 items instead of 4.. the other 2 are there but empty :/

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