Iterating through c# array & placing objects sequentially into other arrays

Question

Okay, so this seems simple, but I can't think of a straightforward solution; Basically I have an object array in C# that contains, say, 102 elements. I then also have 4 other empty arrays. I want to iterate through the original array and distribute the 100 elements evenly, then distribute 101 and 102 to the 1st and 2nd new arrays respectively.

int i = 1,a=0, b=0, c=0, d = 0;

foreach (ReviewStatus data in routingData)
{
    if (i == 1)
    {
        threadOneWork[a] = data;
        a++;
    }
    if (i == 2)
    {
        threadTwoWork[b] = data;
        b++;
    }
    if (i == 3)
    {
        threadThreeWork[c] = data;
        c++;
    }
    if (i == 4)
    {
        threadFourWork[d] = data;
        d++;
        i = 0;
    }
    i++;

}

Now the above code definitely works, but I was curious, does anybody know of a better way to do this??

Jimmy · Accepted Answer · 2011-12-21 19:48:26Z

5

var workArrays = new[] { 
    threadOneWork,
    threadTwoWork,
    threadThreeWork,
    threadFourWork, 
};

for(int i=0; i<routingData.Length; i++) {
    workArrays[i%4][i/4] = routingData[i];
}

answered Dec 21, 2011 at 19:48

Jimmy

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5 Comments

msarchet Over a year ago

That's actually kinda sexy ;)

Jimmy Over a year ago

math can make a lot of sense sometimes.

ChaosPandion Over a year ago

@msarchet - I wouldn't go so far as to say "sexy" but I would say "moderately attractive"...

msarchet Over a year ago

@ChaosPandion it just so obviously simple. and there's no LINQ which is always fun.

spacebed Over a year ago

haha thanks for all the suggestions guys, this is definitely going to be used instead of my original post. LINQ was going to be my next step, but if i don't need it, even better!

Sergey Kalinichenko · Accepted Answer · 2011-12-21 19:47:11Z

2

Put the four arrays into an array of arrays, and use i%4 as an index. Assuming that thread###Work arrays have enough space to store the data, you can do this:

var tw = new[] {threadOneWork, threadTwoWork, threadThreeWork, threadFourWork};
var i = 0;
foreach (ReviewStatus data in routingData) {
    tw[i%4][i/tw.Length] = data;
    i++;
}

answered Dec 21, 2011 at 19:47

Sergey Kalinichenko

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2 Comments

Adam Over a year ago

Are we correct in assuming you mean a multidimensional array [,] as opposed to a jagged array [][]?

Sergey Kalinichenko Over a year ago

@codesparkle I wrote "array of arrays" rather than "multidimensional array" to make this distinction. I just added a code example to clarify.

ΩmegaMan · Accepted Answer · 2011-12-21 20:02:52Z

0

Linq is your friend! Use modulo to group the items via the total number of arrays in your case 4.

For example the code splits them up into four different lists:

var Items = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

Items.Select( ( i, index ) => new {
                                      category = index % 4,
                                      value = i
                                  } )
        .GroupBy( itm => itm.category, itm => itm.value )
        .ToList()
        .ForEach( gr => Console.WriteLine("Group {0} : {1}", gr.Key, string.Join(",", gr)));
/* output
Group 0 : 1,5,9
Group 1 : 2,6,10
Group 2 : 3,7
Group 3 : 4,8
*/

answered Dec 21, 2011 at 20:02

ΩmegaMan

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1 Comment

ΩmegaMan Over a year ago

One note, one doesn't have to create arrays ahead of time. The foreach could be used to do the processing you seek. More compact IMHO; but glad you appreciated it. :-)

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