CODEWITHSUNDEEP
c#
Timisorean
Timisorean

Reputation: 1506

C#: Unexpected output

I have this code: 

static int[] a = {0 , 10 , 20, 30, 40};

public static void Main()
{
    for (int i = 0; i < 10; i++){
        int[] array = a;
        for (int j = 1; j < array.Length; j++)
            array[j] += array[j - 1];

        Console.WriteLine(array[4]);
    }
}

In the console I get the following result:

100
200
350
560
840

But I did not expect this or it is not what I want. I wanted the following result: 

100
100
100
100
100

I have no idea why this is happening. How can I solve this?

Upvotes: 0

Views: 154

Answers (4)

veliyetisgengil
veliyetisgengil

Reputation: 101

Your problem is object referance. You can try this.

 for (int i = 0; i < 10; i++)
        {
            int[] array = new int[5];

            for (int e = 0; e < array.Length; e++)
            {
                array[e] = a[e];
            }

            for (int j = 1; j < array.Length; j++)
                array[j] += array[j - 1];

            Console.WriteLine(array[4]);
        }

Upvotes: 1

S.Cheginy
S.Cheginy

Reputation: 424

Use this: int[] array = a.ToArray(); instead of int[] array = a;

An array in c# is a reference type not value type like int, so when you set a into an array, a and array are same object.

Upvotes: 0

gandalf
gandalf

Reputation: 470

You can clone the array 

static int[] a = { 0, 10, 20, 30, 40 };

public static void Main()
{
    for (int i = 0; i < 10; i++)
    {
        int[] array = (int[])a.Clone();
        for (int j = 1; j < array.Length; j++)
            array[j] += array[j-1];

        Console.WriteLine(array[4]);
    }
}

Upvotes: 0

fhcimolin
fhcimolin

Reputation: 614

It seems that by doing int[] array = a you're dealing with the reference of a, so each time you modify array (in the j for loop) you're updating the a array. In the next loop the value of a will stay with the previously updated value.

Have a look at the Copy method.

Upvotes: 3

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