CODEWITHSUNDEEP
c#
Jose3d
Jose3d

Reputation: 9277

Convert numeric sequences to ranges

I have the following string in C#:

string a="1,2,3,4,5,6,7,8,9,10,22,45,66,88,100,101,102,103,104,105,140,199";

I would like to generate the following output:

1-10,22,45,66,88,100-105,140,199 grouping the consecutive numbers into ranges on this way

"initialnumber-endnumber" and leaving the others as it is.

Could you give me a hand on this?

Thanks in advance.

Upvotes: 2

Views: 988

Answers (2)

Jodrell
Jodrell

Reputation: 35756

okay, first step, enumerate string as ordered integers.

var numbers = a.Split(',').Select(int.Parse()).OrderBy(i => i);

So, then we could use these two functions to enumerate the ranges like this.

private static string RangeToString(int first, int last)
{
    if ( last != first )
    {
        return string.Format("{0}-{1}", first, last);
    }
    else
    {
        return last.ToString();
    }
}

private static IEnumerable<string> GetRanges(IEnumerable<int> numbers)
{
    var last = numbers.First();
    var first = last;
    foreach(var number in numbers.Skip(1))
    {
        if (lastNumber + 1 != number)
        {
            yield return RangeToString(first, last);
            first = number;
        }

        last == number;
    }

    yield return RangeToString(first, last);
}

Then we can put it together like this,

public static string GetRangedList(string list)
{
    var numbers = list.Split(',').Select(int.Parse()).OrderBy(i => i);
    return string.Join(",", GetRanges(numbers));
}

Which obviously you would call like this

var b = GetRangedList(a);

Upvotes: 1

SLaks
SLaks

Reputation: 888293

IEnumerable<string> Rangify(IList<int> input) {
    for (int i = 0; i < input.Count; ) {
        var start = input[i];
        int size = 1;
        while (++i < input.Count && input[i] == start + size)
            size++;

        if (size == 1)
            yield return start.ToString();
        else if (size == 2) {
            yield return start.ToString();
            yield return (start + 1).ToString();
        } else if (size > 2)
            yield return start + " - " + (start + size - 1);
    }
}

Upvotes: 6

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