How do i loop string array in c# more than once?

Question

I can't quite figure it out how to loop through string array after the first initial loop has been done.

My code right now is:

    string[] assignments = new string[] {"A", "B", "C", "D", "E", "F"};

    Array.Resize<string>(ref assignments, 99);
    for (int i = 0; i < 99; i++)
    {
    Console.WriteLine(assignments[i]);
    }

However, it seems that Resizing the array doesn't accomplish much, since arrays values after the 6th value is non-existant. I need it to keep looping more then once: A B C D E F A B C D E F ... and so on, until the limit of 99 is reached.

Do you want your array to contain those repeated items?

Oguz Ozgul
– Oguz Ozgul

2017-10-30 14:01:56 +00:00
Commented Oct 30, 2017 at 14:01 — Oguz Ozgul
– Oguz Ozgul, Commented Oct 30, 2017 at 14:01

Igor · Accepted Answer · 2017-10-30 14:05:20Z

6

Use the mod operator.

string[] assignments = new string[] {"A", "B", "C", "D", "E", "F"};
for (int i = 0; i < 99; i++)
{
    Console.WriteLine(assignments[i % assignments.Length]);
}

.net fiddle

edited Oct 30, 2017 at 14:05

answered Oct 30, 2017 at 14:01

Igor

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1 Comment

Igor Over a year ago

@DmitryBychenko - fair enough. Updated.

Zeph · Accepted Answer · 2017-10-30 14:01:38Z

2

You can use the modulus operator which "computes the remainder after dividing its first operand by its second."

void Main()
{
    string[] assignments = new string[] {"A", "B", "C", "D", "E", "F"};

    for (int i = 0; i < 99; i++)
    {
        var j = i % 6;
        Console.WriteLine(assignments[j]);
    }
}

0 % 6 = 0
1 % 6 = 1
...
6 % 6 = 0
7 % 6 = 1   
... etc.

answered Oct 30, 2017 at 14:01

Zeph

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Comments

Tim Schmelter · Accepted Answer · 2017-10-30 14:15:49Z

2

The obligatory LINQ solution, this extension comes in handy:

public static IEnumerable<T> RepeatIndefinitely<T>(this IEnumerable<T> source)
{
    while (true)
    {
        foreach (var item in source)
        {
            yield return item;
        }
    }
}

Now your task is very easy and readable:

var allAssignments = assignments.RepeatIndefinitely().Take(99);

You can use a foreach-loop with Console.WriteLine or build a string:

string result1 = string.Concat(allAssignments);
string result2 = string.Join(Environment.NewLine, allAssignments)

edited Oct 30, 2017 at 14:15

answered Oct 30, 2017 at 14:10

Tim Schmelter

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2 Comments

Dave Over a year ago

I very much like this. However could it be considered a tad dangerous that the call to repeat indefinitely on its own will crash when it's evaluated?

Tim Schmelter Over a year ago

@Dave: of course it's a bit dangerous, if you f.e. append ToList without a filter (f.e Where or Take) you will get an OutOfMemoryException. But since the name is pretty clear you should know what will happen if you try to take an infinite number of items ;-)

wctiger · Accepted Answer · 2017-10-30 14:05:49Z

0

How about using mod

string[] assignments = new string[] { "A", "B", "C", "D", "E", "F" };

        for (int i = 0; i < 99; i++)
        {
            Console.WriteLine(assignments[i%6]);
        }

answered Oct 30, 2017 at 14:05

wctiger

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