Range division in c#

Question

divide range values into groups, for example if the range between 0 and 100 and i have four groups A,B,C,D. if i want to divide the range into four groups like 0-25 group D 26

Answer 1

Here is some more sample code to help you out:

var groups = new[] { "A", "B", "C", "D" };

//Range size and group size is configurable, should work with any range.
var range = Enumerable.Range(0, 1000).ToArray();
var groupSize = range.Length / groups.Length;

// Here we split range in groups. If range size is not exactly divisible
// to groups size, all left elements go to the last group, then we form
// a dictionary with labels as keys and array of numbers as values
var split = range
    .GroupBy(c => Math.Min(c / groupSize, groups.Length - 1))
    .ToDictionary(c => groups[c.Key], c => c.ToArray());

Console.WriteLine(String.Join(" ", ranges["A"]));   

Answer 2

You could try something like:

    var someNumbers = new [] { 10,67,45,26,78,53,12,45,68};
    var groupNames = new [] { "A", "B", "C", "D" };

    //                               Key                      Value
    var result = someNumbers.GroupBy(v => groupNames[v / 25], p => p);

    foreach(var v in result.OrderBy(i => i.Key))
    {
        Console.WriteLine(v.Key);
        foreach(var k in v)
            Console.WriteLine("  " + k);
    }

I group the values on value / 25 which will be an integer divide and group the values on portions of 25. For example: value 13. 13 / 25 = 0 so 13 will be grouped by 0. For example: value 67. 67 / 25 = 2, so it will be grouped by 2.

The only problem is, that if the value exceeds 99, you get a IndexOfOutBoundsException.

This might be more safe:

public static void Main()
{
    var someNumbers = new [] { 10,67,45,26,78,53,12,45,68};
    var groupNames = new [] { "A", "B", "C", "D" };

    var result = someNumbers.GroupBy(v => v / 25, p => p);

    foreach(var v in result.OrderBy(i => i.Key))
    {
        // check if the key can be used as index for the name array.
        if(v.Key >= groupNames.Length)
            Console.WriteLine(v.Key + " no name for that");
        else
            Console.WriteLine(groupNames[ v.Key]);

        foreach(var k in v)
            Console.WriteLine("  " + k);
    }

}

Look here for a live demo: https://dotnetfiddle.net/8XElaZ